Manchester United's Europa League squad departed for Germany on Sunday without defender Phil Jones.
Jones was initially included in the updated 30-man squad for the competition's resumption named by manager Ole Gunnar Solskjaer last week, but was not present as the team left for Cologne.
The versatile defender has been struggling with a knee injury over recent months, with just eight appearances to his name across all competitions during the 2019/20 season.
Jones has not played at all since January's 6-1 FA Cup thrashing of Tranmere Rovers and will now miss the climax of United's Europa League campaign as he continues to work his way back to fitness.
"Phil has been following an individualised training programme during the post-lockdown period to optimise recovery from a knee problem," Solskjaer told United's official website.
"It was a good opportunity as we had sufficient cover in defensive positions for the remaining Premier League games and he will continue to work with a fitness coach at the Aon Training Complex, while the squad are in Germany."
After wrapping up a dominant 7-1 last-16 aggregate win over Austrian side LASK Linz courtesy of a 2-1 second-leg victory at Old Trafford on Wednesday night, United return to action in a one-legged quarter-final tie against Danish outfit FC Copenhagen at the RheinEnergieStadion on Monday evening.
The winners of that contest will then face either Wolves or Sevilla in the last four, before the final takes place in Cologne on August 21.
Both the 2019/20 Champions League and Europa League competitions are being finished in summer mini-tournaments held in one specific country as a result of the delays caused by the coronavirus pandemic.
