Louis van Gaal confirmed after last night's narrow victory over Valencia that he is sweating on the fitness of three first team stars.
Jonny Evans, Antonio Valencia and Luke Shaw all missed the 2-1 victory, and face a race against time to be fit to feature in the opening home game with Swansea City on Saturday.
More from Louis van Gaal on the injured trio of Evans, Shaw and Valencia: "We have to wait to see if they can play on Saturday." #REUTD14— Manchester United (@ManUtd) August 12, 2014
Strikers Robin van Persie and Danny Welbeck also missed out on the game through their own fitness worries, and their status for the game against the Swans remains unclear.
That was known ahead of the Valencia game however, and the fresh triple blow will be of added concern to Louis van Gaal.
The biggest concern will be Antonio Valencia's fitness, with Rafael da Silva already nursing a groin strain, the Reds are short of cover on the right.
Luke Shaw missing out on making his home debut would also be a disappointment, although United's young defenders Reece James and Tyler Blackett have emerged as options after impressive displays in pre-season, with both featuring last night.
Who is United's biggest concern heading into the weekend?