Having arrived at Old Trafford earlier this summer from Borussia Dortmund in a wave of excitement, it's fair to say that it's been a sluggish start to life at Manchester United for Henrikh Mkhitaryan.
Mkhitaryan picked up the injury following a collision with Marek Suchy during Armenia's friendly with Czech Republic on Wednesday night, as seen in the video below.
The attacking midfielder is yet to start a competitive game since moving to United from Borussia Dortmund during the close-season, but his potential absence from the top-of-the-table clash is unlikely to improve Jose Mourinho's mood over his reunion with opposite number Pep Guardiola taking place immediately after the worldwide break.
However, the Armenian global made a big impact against Hull City in their last league match, helping his side pick up three more points at the KCOM Stadium.
Mourinho, who has allowed striker Zlatan Ibrahimovic extra-time off, voiced concerns about the worldwide break earlier this week.
The match has the added spice this year of being the first time Mourinho will face his old foe Pep Guardiola since the former La Liga rivals started at their new clubs in the Premier League.
"We keep eight outfield players and Sam Johnstone as the goalkeeper", he told MUTV.