The Gunners headed into the reverse league fixture at Old Trafford on a 19-match unbeaten run in all competitions, whereas United were lurching from one dreadful performance to another under then-boss Jose Mourinho.
It has been all change since then from the Red Devils' perspective, though, as they are the team with all the momentum on their side now, making up an 11-point deficit on the top four to occupy the final Champions League spot heading into this huge match.
Ahead of Sunday's clash at the Emirates Stadium, Sports Mole selects the strongest combined XI from both teams using only the players expected to be available for selection.
Petr Cech showed his quality once again on his return to former club Rennes on Thursday night, producing a couple of top-class saves to potentially rival Bernd Leno for a start on Sunday. However, neither keeper comes close to matching the quality of David de Gea, who has recovered from a disappointing few months midway through 2018 to show why he is regarded as the best goalkeeper on the planet.
Arsenal are not exactly blessed with options in the full-back departments, especially since Bellerin was ruled out for nine months at the turn of the year. Ashley Young started in a more advanced wing position for United against Paris Saint-Germain in midweek but has now become more used to filling in at right-back, though his grip is surely slipping following the emergence of Diogo Dalot, who looks a real prospect. Luke Shaw has finally managed to add some consistency to his game on the opposite flank, meanwhile, producing his best display since a long-term layoff in the recent 0-0 draw with Liverpool.
It is easy to forget that just a few months ago, around the time these sides last faced off, Victor Lindelof had been written off as a £31m flop, effectively relegated to fourth-choice centre-back. However, the Iceman has been terrific since being given a run of games and could well be in contention for the Red Devils' Player of the Year gong if he keeps up recent displays. Chris Smalling has also performed well alongside Lindelof, while Phil Jones and Eric Bailly have also been used by Ole Gunnar Solskjaer, but we are going to give the nod to Arsenal's Sokratis Papastathopoulos - he was superb at the back against Tottenham Hotspur last week and has started 25 of the Gunners' Europa League and Premier League matches, showing that he has the trust of boss Unai Emery.
United have been badly hit by injuries in midfield, but Ander Herrera is expected to return from injury this weekend and Paul Pogba is also in contention after sitting out the PSG match through suspension. Pogba's inclusion needs no justification, having arguably been the division's best player in 2019, while Herrera has proved his true quality over the same timeframe, putting his shuttling abilities to good use. In terms of the defensive midfielder to hold it all together, Nemanja Matic is unlikely to be fit this weekend and Torreira is suspended, so Granit Xhaka gets the nod almost by default.
Antony Martial is another player expected to return from a month-long spell on the sidelines this Sunday - bad news for Arsenal as he has scored in back-to-back games against them. Assuming he is fit, the Frenchman provides something a little different out wide, which should help to get the best out of Alexandre Lacazette. Now preferred to Pierre-Emerick Aubameyang through the middle in the Premier League, Lacazette is looking to become only the second Arsenal player to score in six consecutive home Premier League games after Thierry Henry. That leaves one more spot up for grabs, which Marcus Rashford gets ahead of Romelu Lukaku by virtue of his mobility in the wide areas.