How will Manchester United line up against Arsenal if Nemanja Matic misses out?

Manchester United eased past Marco Silva's Watford side on Tuesday (28 November), the eighth time they have scored four in a single match this season. And it still wasn't good enough to inch closer to Manchester City. A last minute winner from Raheem Sterling against Southampton on Wednesday [30 November] ensured the gap between the two city rivals was restored to eight points with the two set to meet at Old Trafford in 10 days.

The gap could conceivably be bigger by then. City's final game before the derby is at home to David Moyes' beleaguered West Ham United, fresh from shipping four to Everton. United meanwhile head to north London to renew hostilities with Arsenal – the team who halted their 25-match unbeaten run in the league last May.

A 4-2 win over Watford was a good-warm up, but that win may have come at a cost with Nemanja Matic limping off in the second-half with what his manager described as a muscular problem. United are yet to officially rule the Serbia international out, but his manager's comments in the aftermath of Tuesday's win were ominous. "For Matic to tell me he wants to be replaced – he does not do that if it is nothing important."

Prior to that withdrawal after 54 minutes, Matic had been ever-present in United's Premier League starting XI, holding things together in the collective absences of Paul Pogba, Marouane Fellaini and Michael Carrick. Missing out on Saturday [2 December] would act as an enormous blow.

Not helping matters, one of the candidates to replace the Serbian could be a further injury doubt. Fellaini was omitted from the United squad on Tuesday night with Mourinho explaining ahead of kick-off the former Everton midfielder had picked up a knock. He added he wasn't sure if it meant he would miss Saturday's game, with reports from Belgium suggesting Fellaini was suffering from a knee problem – although it is not yet known if it was the same issue which saw him miss the entire month of October.

Those decisions over Matic and Fellaini should be seen as precautionary measures at this point but Ander Herrera would usually be the direct option to replace the former if he is not ready in time. Herrera, who has struggled to replicate the form that saw him win United's Player of the Season award last term, came onto replace Matic against Watford on Tuesday – coinciding with the period where his side lost control and conceded two goals. Scott McTominay is another option.

In terms of shape; we have seen increasingly more of the 3-5-2 or a 3-4-3 this season, particularly against opposition who line up similarly like Spurs did at Old Trafford in November and Watford midweek. Ashley Young continues to prove his worth at left wing-back with Antonio Valencia's spot on the other side a given but is in defence where decisions are to be made. Phil Jones and Eric Bailly have not played since before November's international break. A combination of Chris Smalling, Marcos Rojo and Victor Lindelof or all three have been used in their absences – Mourinho has previously suggested Bailly had the better chance of returning first out of the two.

Romelu Lukaku's run of just one goal in his last seven league appearances remains a concern but his blossoming understanding with Anthony Martial is starting to bear fruit. For the time being, the France international now appears to be Mourinho's preferred option to support or even play alongside the Belgian having started ahead of Marcus Rashford in United's last four games. Zlatan Ibrahimovic continues to wait for his first start since returning after a six-month layoff.

That leaves one more role in attack up for grabs. Henrikh Mkhitaryan's underwhelming campaign has cost him in recent weeks, having failed to make the squad in three of United's last four games. Mourinho has experimented with bringing Marcus Rashford in with he, Martial and Lukaku starting for the first-time all season in the 4-1 victory over Newcastle United, although Jesse Lingard will be hoping to be in manager's plans. Twice he has started in an attacking midfield role behind Martial and Lukaku this season, scoring twice from there against Swansea City in the Carabao Cup before taking up the same role against Watford on Tuesday, teeing up the Frenchman's strike before scoring his own sublime effort.