It's likely that Manchester United would've expected to use the Europa League as a chance to play the fringe players who don't get much of a chance in league games, however now the situation has changed.
We're now three months into the season and Jose Mourinho's side find themselves at 6th place in the Premier League, six points off 4th, with the five teams above in much stronger form and United dropping a lot of points at home, so Champions League football via a top four spot next season is looking more and more unlikely by the week.
Since UEFA implemented Champions League qualification through winning the Europa League at the start of the 2014/2015 season there has been a lot more interest from every club involved and despite it not being the most coveted European club competition, United will definitely be hungry to win it for the first time in their history. Because of this, it's widely expected that Jose Mourinho will be fielding out a strong side at Old Trafford against the team that beat the Reds in the reverse fixture which really emphasises the Portugese boss's desire to proceed in the competition despite worries that it's affecting league form.
In defence...
Goalkeeper - David De Gea:
This match is a must-win contest, everyone knows it, and the difference in talent between David De Gea and Sergio Romero is too much for the Spaniard to be left out. De Gea has featured in three of United's four Europa League games so far this season so it's likely we'll see him play a part in this one as well. If Romero does miss out tomorrow night, he'll be hoping to start against West Ham United in next week's EFL Cup quarter-final tie however with it being at such a late stage in the competition it's likely that Mourinho keep him as backup.
Right-back - Matteo Darmian:
It was reported by Manchester Evening News on Friday afternoon that Antonio Valencia had made a miraculous recovery from a broken wrist suffered just three weeks ago and was available for the match against Arsenal, the Ecudorian went on to play the match and was awarded Man of the Match. He looks a new man under Mourinho's guidance however it would probably be safer to not risk him here and play him after a full weeks rest against West Ham United on Sunday. The man to take his place should be Matteo Darmian, the versatile full-back has been brought in while Valencia's been on the sidelines and he's also played in three of United's four Europa League games so you shouldn't be suprised if he's given another start tomorrow.
Centre-back - Phil Jones:
Since being hinted as the future of England's defence by Sir Alex Ferguson back in 2011, Phil Jones' United career hasn't really set off mainly due to injuries but Jose Mourinho has expressed his interest in the 24 year old's talents since taking charge. A lot of football fans forget that he's still relatively young and yet to hit his prime just because he's been at the club for a long period of time and despite concerns with his aerial ability, his first two performances after returning from an injury sustained at the start of the season have been up to standard. Jones still has a lot to prove to the fans and manager while Eric Bailly and Chris Smalling are injured but he's definitely on the right track.
Centre-back - Marcos Rojo:
Fans of Manchester United were in shock when Marcos Rojo survived the summer and a large number still want him out today however the Argentinian is showing slight signs of the player Louis van Gaal signed in his new role at centre-back in the last few games he's started. He's playing like his United career depends on it at the moment, and in reality it is, alongside Phil Jones at the back and he'll be desperate to keep on improving with the January transfer window fast approaching. The fact that there is only really one more realistic centre-back option in Daley Blind at this moment in time helps Rojo's case in this match because it's expected that the Dutchman will start at left-back.
Left-back - Daley Blind:
The left-back position is quite possibly the hardest position to predict at the moment because lets be honest it could be Blind, Shaw, Darmian or even Young starting there tomorrow night. Daley Blind has been benched in the last two matches but he started against Fenerbache in United's last European match so it's up in the air whether he'll start again here. The Dutch defender is said to be the best left-back in the squad right now while Luke Shaw is being put in and out of matchday squads and is mainly potential anyway so he'll definitely play a part be it in the starting lineup or off the bench.
In Midfield...
Centre-midfield - Ander Herrera:
Herrera has been a regular starter this season after two seasons being mainly a second choice midfielder and it's fair to say he's enjoying himself, the fans have taken to the Spaniard's passion for the club and his will to succeed as well which is really helping his confidence. Ander is currently playing a pivotal role in Mourinho's plans so far this season and with Marouane Fellaini injured while Morgan Schneiderlin is out of favour it's looking like he'll be given another start in this one. United need to victory and in times of need he can really up the tempo of games and make that transition from defending to attacking much quicker than someone like Michael Carrick who is likely to be rested for the West Ham United game on Sunday.
Centre-midfield - Paul Pogba:
The French midfielder has almost played in every game since rejoining his childhood club in the summer and due to the shortage in realistic midfield options it looks like he'll feature here as well. Pogba has noticeably been improving for club and country after waves of critism in his first couple of months and is really becoming the engine of the team, having Carrick alongside him visibly gives him a lot more freedom to play his own game so it'll be interesting to see if he can keep up the impressive form without the English anchorman. He's Manchester United's top goalscorer so far in the competition after scoring twice in the last European home game against Fenerbache so he'll be hoping to keep it up and will be hungry to contribute more as the club attempt to prevent an early exit.
In Attack...
Right-midfield - Jesse Lingard:
We haven't seen Jesse Lingard since Burnley visited Old Trafford where he was taken off midway through the 2nd half after a below par performance. The Manchester-born winger has played in two of the four Europa League matches this season and scored a brilliant 4th goal against Fenerbache at Old Trafford so he could very well be brought back into the side. United outcast Henrikh Mkhitaryan is unlikely to be called upon and he'll be on the bench at best while Marcus Rashford, who is wrongly seen as a wide man by Mourinho had a game to forget against Arsenal and was arguably the cause of the late equaliser.
Centre-attacking-midfield - Juan Mata:
'Who's the best player in the Premier League? It's you Juan Juan Juan, it's you Juan Juan' has been a common chant in the Stretford End this season after Juan Mata has put on a number of dazzling displays and is the player of the seasonso far for many Reds. The little Spaniard has adapted to Jose Mourinho's game perfectly and even though he is still playing on the right at times, it isn't just as a winger but more of an inside forward which is resulting in him scoring a lot of important goals. Jose might be keen to rest Mata for the West Ham United match on Sunday however because of the importance of the game it'll be nice to see him back in his position just behind the striker where he's at his best.
Left-midfield - Anthony Martial:
Martial was bright at times against Arsenal but still really struggled to make an impact like all season and seems slightly out favour by Jose Mourinho. It wouldn't be a suprise if Ashley Young replaced him or even Memphis is given an opportunity but it's clear that the young French forward just needs a good run of games in order to replicate last season's form. If Zlatan Ibrahimovic was to start, though, it's likely that Lingard will take his place on the left while Mata is on the right and Rooney just behind so Anthony Martial will be hoping that the Swede is rested for a couple more days.
Striker - Wayne Rooney:
After a really impressive showing against Swansea City where he bagged three assists but the Manchester United and England captain had to settle for a place on the bench amid controversy over joining a wedding party and looking worse for wear in early hours while on international duty. It's unlikely that the manager will rush Zlatan back into the team after the veteran striker hasn't been training for three weeks now so making him train this week and keeping him until Sunday is probably the best bet, leaving Wayne Rooney available to lead the line. The Englishman is just two goals away from passing Sir Bobby Charlton and becoming the Manchester United top goalscorer, he also scored a phenomenal goal in the defeat to Fenerbache in Istanbul so it's expected that Mourinho will stick with his man here.