Does Tuanzebe keep his place?
Even if Manchester United had a world-class centre half to come back in Axel Tuanzebe would take some budging after he duelled with Kylian Mbappe. Tuanzebe is the quickest centre half United have and the ideal complement for Harry Maguire or Victor Lindelof, centre halves in need of a speedy partner.
Lindelof has a knack for performing against elite opponents and did so again in midweek with Tuanzebe and Luke Shaw guarding the channels. That Paris Saint-Germain were devoid of a figurehead played into Lindelof's hands and Chelsea's set-up could be similar, with Timo Werner a floating forward rather than a target man.
Maguire and Lindelof is not a convincing partnership and Alex Telles' tactical flexibility brought about an improvement from Shaw in Paris.
Stick with the back three?
Telles' average positioning in Paris was telling: most of the left wing-back's activity came in the centre and his passing regularly bypassed the PSG midfield into Anthony Martial or Marcus Rashford. Telles' ability to step into midfield enabled United to seamlessly switch to a back four when they did not have the ball without upsetting the fine balance between defence and attack, preparing them for Paul Pogba's introduction and the switch to a 4-3-3.
Fred was colossal in Paris again and Scott McTominay out Ander Herrera'd Ander Herrera. Rashford and Martial had no trouble adapting to the split striker strategy, either.
Or back to a back four?
United used a back three on both trips to Stamford Bridge last season, as well as the neutral venue of Wembley for their FA Cup semi-final, but lined up in a 4-2-3-1 at Old Trafford on the opening weekend and won 4-0. Chelsea, similarly to PSG, command a degree of respect but have an inferior attack and a defence that is just as gettable.
Aaron Wan-Bissaka was picked almost solely to cope with Mbappe and United could do with a right-sided attacker to exploit the space left by Ben Chelsea left-back Chilwell.
Arrest home form?
United are winless in their last four at Old Trafford in the Premier League and were certainly not deserving of victory against Southampton, West Ham, Crystal Palace or Tottenham. Chelsea's record in M16, once respectable in the early years of the Premier League era, is dismal: two wins in the last 13 and their last triumph was in Sir Alex Ferguson's final match before news of his retirement emerged.
Chelsea went about their summer business as though their back five is Cech, Ivanovic, Carvalho, Terry and Cole and it was rather tragicomic the supposedly retired Cech, 38, was listed in their Premier League squad this week.
Who misses out?
Eric Bailly and Jesse Lingard are sidelined for 'weeks' but the United squad is so sizeable Solskjaer must lament the Premier League's decision to have reduced benches back down to seven players. The presence of Brandon Williams and Facundo Pellistri in the Under-23 team last night suggests they will be off duty tonight.
Solskjaer is not transparent with his team news but sounded optimistic about the prospect of Maguire, Edinson Cavani and Mason Greenwood returning. Given the compelling case to name an unchanged side, United could have Henderson, Fosu-Mensah, Maguire, Pogba, Van de Beek, Matic, Mata, James, Cavani, Greenwood and Ighalo in reserve.