Manchester United have confirmed their defender Phil Jones has been sidelined with mild thrombosis and will be out of action for a minimum of three weeks.
The England international last featured in the Red Devils' 2-0 defeat to Paris Saint-Germain in the pre-season friendly. He was not involved in the squad as Louis van Gaal's men sealed a 1-0 victory over Tottenham Hotspur in the season-opener.
United will take on Belgian runners-up Club Brugge in the Champions League play-off in August, as Jones is set to be out of action for at least three weeks. He will miss the European fixtures scheduled for later this month.
"Manchester United defender Phil Jones has been ruled out of action for a minimum of three weeks," a statement read on United's official website.
"It has now been revealed that Jones has mild thrombosis and the blood clotting has forced him to be sidelined for the opening of the campaign. Consequently, the centre-back is expected to miss the two Champions League play-off ties with Club Brugge."
For the first match of the 2015/16 season against Tottenham, Van Gaal fielded Chris Smalling and Daley Blind in the heart of the defence. The England international was impressive alongside the former Ajax man.
With Jones ruled out for a minimum of three weeks, Van Gaal will have Smalling, Blind, Marcos Rojo, Jonny Evans and Paddy McNair as his first choice centre-backs in the squad.
Since Van Gaal celebrated his 64th birthday on 8 August, the Dutchman was delighted after United sealed three points against Tottenham Hotspur. Kyle Walker's own goal in the first half was the difference between the two sides in the end.
"Today was very special because it was also my birthday and my children are here and my grandchildren are here and when you lose it's not a nice day," Van Gaal explained.
"I wouldn't be able to laugh anymore in spite of my children being here. I will have a good birthday party tonight in my favourite restaurant," he said.