Jose Mourinho Eric Bailly Manchester United Antonio Conte Chelsea
Manchester United defender Eric Bailly comes off injured during the Premier League game against Chelsea as Jose Mourinho (L) and Antonio Conte (R) watch on, October 23, 2016Reuters

To add salt to the gaping what-on-earth-just-happened-there, 4-0-drubbing wounds, Manchester United also lost their best defender of the season so far – Eric Bailly – to injury on Sunday. And according to the manager Jose Mourinho the early signs do not look too good.

With Manchester United trailing 2-0, Bailly was forced off in the 52nd minute, with a knee injury. As Chelsea went on to smash in two more goals to complete a comprehensive victory on Mourinho's return to Stamford Bridge, there were also concerns over how serious Bailly's injury could be.

According to Mourinho, it looks like the Ivory Coast international could be set for a concerted spell on the treatment table.

"He is injured and I am afraid he is badly injured," Mourinho told reporters. "In his knee, in the ligament area. He feels it is really bad."

Manchester United, even with Bailly in the lineup, have had defensive issues, but with the summer signing now set to be out, Mourinho will have to figure out a way to tighten up his defence. It doesn't get any easier for Manchester United, though, because next up is Manchester City in the EFL Cup fourth round on Wednesday.

Mourinho could also be without Marouane Fellaini, who did not come out in the second half after being on the receiving end of a nasty tackle from David Luiz, while Wayne Rooney was absent from the matchday squad against Chelsea owing to a knock picked up in training.

Those are headaches Mourinho could have done without after suffering what was his biggest defeat as a Premier League manager. "I would prefer to play in the Premier League," Mourinho said when asked about the City match next up. "It's a bad feeling in the Premier League. With the combination of results the gap to the top is six points. We've had a very difficult period of matches.

"We are really, really sad but again this is not for kids, this is for men and tomorrow we have to be men and work for the next one."