Manchester United manager Jose Mourinho admits he is unsure what his best back four is after a tough start to the Premier League season.
Mourinho is under fire after United suffered a second loss in three league games with their 3-0 defeat to Tottenham at Old Trafford on Monday.
The Portuguese tactician is yet to start the same defence in any two games this campaign, with only left-back Luke Shaw starting all three matches and midfielder Ander Herrera used at centre-back against Spurs.
Asked if he knew what his best defence was, Mourinho accepted he was unsure.
"Why not? Because in the first game [it was Victor] Lindelof and [Eric] Bailly," he said.
"Today played [Phil] Jones and [Chris] Smalling, but now Jones is injured, and next match it will be Smalling, with another one.
"When Marcos Rojo comes he will be an option, and no, I don't know my best back four."
United will look to bounce back when they visit Burnley on Sunday.