Espanyol have lost their last three in the league to drop down to seventh position in the table, while Barcelona currently top the pile on 28 points, one point ahead of second-placed Sevilla.
A six-game unbeaten run between September 25 and November 11 included four wins, and left Espanyol in the top four. At that point, Rubi's team were showing signs that they could be surprise challengers for a Champions League position in Spain's top flight during the 2018-19 campaign.
Espanyol's last victory in the league was a 1-0 success over Athletic Bilbao at the start of last month, however, and since then they have lost three straight matches against Sevilla, Girona and Getafe. As a result, they currently sit seventh in La Liga entering the latest round of matches.
That said, the Catalan outfit are just three points off the top four, and just seven off leaders Barcelona. The likes of Valencia and Villarreal have struggled this season, which could mean that a top-six finish is a very real possibility for Espanyol.
Periquitos ended last season in 11th spot in La Liga, and they have not actually finished higher than eighth since the 2004-05 campaign, which brought fifth spot. It is important that head coach Rubi steadies the chip following a poor run, but matches do not come more difficult than Barcelona.
Espanyol have a tough finish to 2018 when considering that their three matches before the winter break are against Barcelona, Real Betis and Atletico Madrid. The Catalan outfit only just squeezed into the last-16 stage of the Copa del Rey, meanwhile, with an away-goals victory over Cadiz on Tuesday night.
Espanyol might have only scored 17 times in their 14 La Liga matches this season, but they have conceded just 16 times, which is a better defensive record than both Barcelona and Real Madrid.
Saturday night will be a huge occasion for Espanyol, and a win over Barcelona would certainly aid suggestions that they should be targeting a top-seven finish this season.
Recent form: WWWLDW
Recent form (all competitions): DLDWWW
Eight wins, four draws and two defeats - that is how Barcelona have performed in La Liga this season. It has brought them 28 points, which is good enough for first position at this stage.
Dropping points in six of their first 14 league matches of the season is not quite what Barcelona would have had in mind, but it has been a competitive La Liga this term, and they are currently the side at the top of the pile.
Ernesto Valverde's side took care of their business in the Copa del Rey on Wednesday night, recording a 4-1 win over Cultural Leonesa to secure a 5-1 aggregate victory. The holders will be present in the round of 16, and now their attention switches back to the league, which is close to wrapping up for 2018.
Barcelona ran out 2-0 victors over Villarreal at Camp Nou last weekend, and will bring a three-match winning run into Saturday's contest. They will host Tottenham Hotspur in the Champions League next week having already booked their spot in the next round as group winners, before travelling to Levante next weekend.
Barcelona's work for 2018 will end with a home game against Celta Vigo on December 22. The year brought yet another La Liga and Copa del Rey double, but the Catalan outfit will be hoping that they can make a serious play for the Champions League this term.
Valverde's team have not exactly been terrific on the road this season, winning only half of their league matches and scoring just nine times in the process. Espanyol have won five of their six in front of their own supporters, meanwhile, which makes this weekend's contest extremely interesting indeed.
A certain Lionel Messi loves playing against Espanyol having scored 21 times in his 31 appearances against Barcelona's Catalan rivals, and the Argentine has only ever lost one La Liga game against the White and Blues.
Recent form: WDWLLL
Recent form (all competitions): LWLLLW
Naldo and Sergio Garcia remain on the sidelines for Espanyol, but head coach Rubi has no fresh injury concerns. Borja Iglesias is the team's leading scorer this season with eight, and he will again lead the line.
There will also be a spot for in-demand defender Mario Hermoso, who continues to be linked with a move to Real Madrid. Pablo Piatti and Hernan Perez, meanwhile, should be selected in the wide positions.
As for Barcelona, Luis Suarez and Arthur have both recently been on the sidelines with knee and muscular injuries respectively, but the pair trained on Thursday, and are expected to be handed spots in the starting XI for this match.
Espanyol possible starting lineup:
Diego Lopez; Javi Lopez, Duarte, Hermoso, Vila; Perez, Darder, David Lopez, Granero, Piatti; Iglesias
Barcelona possible starting lineup:
Ter Stegen; Semedo, Pique, Lenglet, Alba; Arthur, Busquets, Rakitic; Coutinho, Suarez, Messi
Head To Head
Barcelona's last success away to Espanyol in the league was a 3-0 win in April 2017. Meanwhile, Espanyol last overcame Barcelona in La Liga back in 2009, with that victory occurring at Camp Nou.
Espanyol have not beaten Barcelona on home soil in the league since January 2007.
We say: Espanyol 1-2 Barcelona
It is shaping up to be a very interesting battle on Saturday night. Espanyol have just hit a rocky patch though, and we fancy Barcelona to edge a close match.