The home side were looking for revenge following their 5-1 drubbing at the hands of Miroslav Dukic's men two weeks ago.
Read how all the action unfolded in our commentary below.
5.33pmGood evening and welcome to the live commentary of the Europa League clash between St Gallen and Valencia.
5.35pmSt Gallen will be out for revenge in this game tonight following their 5-1 hammering at the Mestalla two weeks ago, which moved Valencia to within a point of Swansea City at the top of the group.
5.38pmThe team news has been released and we'll start with the home side.
5.42pmST GALLEN STARTING XI: Lopar, Montandon, Besle, Nater, Vitkieviez, Mutsch, Martic, Mathys, Lenjani, Rodriguez, Karanovic
5.45pmVALENCIA STARTING XI: Guaita, Victor Ruiz, Barragan, Ricardo Costa, Romeu, Bernat, Canales, Michel, Cartabia, Jonas, Postiga
5.50pmThe home side have made one change from their team from the reverse fixture two weeks ago as Ivan Martic comes into the side to replace Dejan Janjatovic.
5.52pmMiroslav Dukic has made four changes to his team for this clash as Joao Pereira, Daniel Parejo, Pablo Piatti and Paco Alcacer all make way and are replaced by Antonio Barragan, Michel, Jonas and Helder Postiga.
5.55pmThe players are making their way out onto the field and we should be underway shortly.
1 minWe're underway in this Europa League clash.
2 minSlow start to the game but Valencia dominate the possession as they try to find a passing range. This is highlighted as Barragan looks deep for Postiga but he overhits his pass and the ball goes out for a goal kick.
4 minSAVE! Valencia threaten and Postiga comes close to giving his side the lead as Barragan whips in a cross from the right and the striker goes above his man to control the ball and turn and fire at goal but the keeper makes the save at his near post.
5 minFrom the resulting corner Michel whips in a cross but the home side clear the line with a good header from Mantandon.
7 minCHANCE! St Gallen should be ahead as they work the ball down the right and Vitkieviez whips in a cross from the right, which evades the head of Mathys but falls to Karanovic at the back post and he misses his kick. A shocking miss.
10 minCHANCE! Valencia's turn to threaten again and they move the ball through midfield again before Michel finds Cartabia on the left, in space he shoots at goal but his effort goes just wide of the target.
12 minThe visitors work the ball again and the ball goes wide to Cartabia who takes a touch to work the ball onto his right foot but this time his effort goes well wide of the target.
13 minCHANCE! Postiga comes so close to giving his side the lead as he collects the ball 30 yards from goal and drives a shot with his right foot from about 25 yards out, his effort looks to be heading for the top corner and Lopar doesn't move but his effort goes inches over.
15 minThe home side are struggling to impose themselves in the game and every time they lose the ball upfield the visitors carve out an opening. They need to do a better job of retaining possession.
18 minYELLOW CARD: Ricardo Costa goes into the book for a challenge on Karanovic giving the home side a free kick in a threatening position deep down the left-hand side of the pitch.
19 minRodriguez's free kick is poor as it doesn't get past the first man as Ruiz heads the ball clear and Canales takes the ball past the halfway line before he's tackled to completely change field position.
22 minThe visitors are continuing to dominate possession and appear to be the more dangerous of the two sides at the moment but St Gallen are holding their own defensively.
24 minSUBSTITUTION: An early change for the visitors as Cartabia picks up an injury and is replaced by Piatti.
25 minValencia win a free kick in a promising position down the right as Barragan is brought down just outside the box. Canales stands over the ball about 20 yards from goal.
26 minOFF THE POST! Canales fires his effort at goal and the ball goes over the wall and clatters off the post with Lopar beaten. St Gallen manage to clear the danger before anyone in Orange could pounce. What a strike from the midfielder who is so unfortunate to see his effort hit the woodwork.
28 minAnother free kick in a good position for the visitors as Postiga gets fouled as he turns and tries to run at goal. The referee tries to play advantage but there is none so he awards the free kick. Canales stands over the ball again.
30 minGOAL! St Gallen 0-1 Valencia (Piatti)
30 minThe visitors take the lead as Piatti turns the ball in on the rebound after Canales's free kick hit the post again with a powerful strike. All the St Gallen defence went to sleep allowing the midfielder to get in behind and tap the ball into the net.
32 minSt Gallen try to get back into the game immediately as Karanovic finds space in the right inside channel and runs to the dead ball line but when he tries to lift an effort into the area Guaita claims it with ease.
35 minThe home side have responded to going behind quite well and have upped their passing tempo and the ball is seemingly being used a lot more in the Valencia side of the field.
37 minGOAL! St Gallen 1-1 Valencia (Besle)
37 minSt Gallen are level as Besle heads home from a corner as Rodriguez plays it short and gets a return and whips a ball to the back post where Montandon heads back into the middle and the defender rises highest in the six-yard box to nod it home.
38 minThat goal was coming as the home side really upped the ante in the last five minutes or so and the pressure finally told on the Valencia defence.
41 minValencia are really struggling to get their passing game back into rhythm after they dominated the opening 30 minutes. They haven't been the same side since they took the lead, they may have taken their foot of the pedal and that has allowed the home side back into the game.
43 minYELLOW CARD Postiga goes into the book for a challenge on Besle. He hasn't been able to hold the ball as well as he did in the early stages and that has been one of the reasons his side's performance has dropped off.
45 minThere will be two minutes of added time.
45 + 2 minHALF-TIME: St Gallen 1-1 Valencia
6.50pmThe half ends all square and it really was a strange 45 minutes as Valencia dominated the game for the opening 30 until after Piatti gave them the lead. From then on St Gallen upped the ante and put the visitors under pressure until Besle got the equaliser.
6.53pmValencia really struggled to find their momentum again after taking the lead and St Gallen saw the weakness and struck back with a well worked corner routine. The game is well and truly in the balance but if the visitors can get back into their rhythm they have shown they have the quality to get goals.
6.55pmMore importantly for Valencia is the news that they can go top of Group A with a win tonight as Swansea could only draw against 10-man Kuban Krasnodor. Read our report of that game here.
46 minWe're back underway in this Group A clash.
48 minThe visitors move the ball well to begin the half and Postiga manufactures half a yard of space and fires an effort at goal but Lopar easily claims his tame effort.
50 minCanales brings down Lenjani down the right allowing the home side to earn a free kick in a dangerous area of the pitch about 35 yards from goal.
51 minRodriguez takes the free kick but his delivery is poor and is cleared with ease by the Valencia defence.
53 minPiatti raids down the right and digs out an excellent cross which flashes across the face of goal but no player in orange is there to turn the ball home.
54 minSHOT! Karanovic finds space in the middle of the field and he collects the ball from Mathys, he fires a powerful shot at goal but Guaita makes the save.
56 minPENALTY TO VALENCIA!
56 minRED CARD! Montandon is sent off for the home side as he pulls back Jonas in the area when he was bearing down on goal leaving the referee with little option but to dismiss him.
57 minPENALTY SAVED! Jonas takes a long run up and fires his effort low into the corner but Lopar gets down to his left and saves the ball with ease, holding it to stop the rebound. Not a great spot kick.
58 minThat miss could be crucial for the visitors's hopes of winning the game but the hosts have been reduced to 10 men so you think there could be more chances to come their way.
60 minJonas tries an effort from distance to try and make amends for his miss from the spot but he fires his shot wide of the target. That effort didn't have much going for it.
62 minValencia's rhythm seems to have been disrupted by the penalty miss but this time the home side may not be able to take advantage due to their lack of numbers up front.
65 minGOAL! St Gallen 2-1 Valencia (Karanovic)
65 minThe home side take the lead with a brilliant individual goal from Karanovic. As he races onto a clearance and beats the tackle of Ruiz before knocking the ball through the legs of Costa and beating him in a foot race, then he drives into the box and fires an effort past Guaita. Marvellous work from the striker.
66 minThat could be a game winner for St Gallen and if it is that goal deserves to win most games. A brilliant solo effort from Karanovic but do Valencia have an answer for it?
68 minAnother chance to threaten for the home side as they win a free kick around 25 yards from goal and Vitkieviez steps up to take it but he can't get his effort on target as he fires his shot wide of the post.
70 minOFF THE POST! Valencia hit the woodwork for the third time in the game as Postiga takes a touch inside the area and drills a low effort at goal, he gets it through a crowd of players but the post denies him with Lopar beaten.
72 minIt was all hands to the pump their for St Gallen and you get the feeling it maybe that way for the next 20 minutes or so.
73 minValencia work the ball well down the left and Canales is presented with a channel to run into and he does just that and unleashes an effort at goal but his shot is too high and goes over the bar.
75 minGOAL! St Gallen 2-2 Valencia (Piatti)
75 minPiatti gets his side level with his second goal of the game as he fires home from close range after a scramble in the penalty area as Canales first shot was blocked back into his path and he rifled a left-footed effort into the bottom corner through a crowd of players.
77 minPressure finally told on the St Gallen goal as Valencia found their rhythm once again and began to work the defenders out of position and they appeared to have a shoot on sight mentality. The home side will be praying they can hold onto a point here.
79 minBarragan raids forward from right back and decides to have a crack at goal, his effort looks to be goalbound but Besle gets in the way of his shot to make a crucial block. The home side will have to make a lot more of them in the last 10 minutes.
81 minValencia work the ball in the final third again and this time the ball comes to the other full back Bernat and he lines up an effort but his shot is blocked by Mutsch, who looks to be in pain but at least he got there to make the stop. That's the sort of mentality St Gallen need.
83 minSt Gallen get a slight respite as Canales commits a foul in his desperation to win the ball back in the final third. There are a lot of tired players out on the pitch at the moment.
85 minGOAL! St Gallen 2-3 Valencia (Canales)
85 minValencia retake the lead and what a goal from Canales to earn it. He collects the ball 30 yards from goal and turns immediately onto his left foot and he strikes a curling effort into the bottom corner of the net, leaving Lopar with no chance.
87 minSt Gallen are handed a chance to get back into the game immediately as Ruiz brings down Martic 25 yards from goal and Wuthrich stands over the ball.
88 minWuthrich gets his strike off and his effort gets over the ball but it doesn't really trouble Guaita who makes a comfortable save.
90 minThere will be three minutes of added time.
90 + 3 minFULL-TIME: St Gallen 2-3 Valencia
7.51pmValencia secure the victory and will move to the top of Group A after coming from behind to beat St Gallen thanks to a brace from Pablo Piatti and a wondergoal from Sergio Canales.
7.53pmThanks for joining our commentary of this game be sure to check out our other commentaries of the Europa League this evening.