It’s been an eventful first-half so far between Arsenal and Chelsea in the second leg of the League Cup semifinal at the Emirates, but unfortunately for Chelsea, one of those events involved Willian picking up and being forced off with some sort of a knock. It was certainly a non-contact injury, and most reports are calling it a hamstring, which could see Willian miss not-insignificant amount of time.
Willian limps off..... Possible hamstring strain.— Ben Dinnery (@BenDinnery) January 24, 2018
 Barkley on for his Chelsea debut [and] his first competitive game of 2017/18. #CFC
Willian started as one of the all-smalls front three for Chelsea, and he’s been replaced by January arrival Ross Barkley. It is the former Everton’s man Chelsea debut, and it didn’t take him long to be involved, being on the receiving end of a shocking Jack Wilshere tackle (rewarded only with a yellow when a red would not have gone amiss) and then committing a bit of a rash challenge himself on Koscielny that gave Arsenal a free kick in a dangerous position (which Chelsea’s wall defended well enough).
Willian had been working on Premier League-best appearance streak (50 in a row) and had missed just one of Chelsea’s last 69 games. He’ll probably take a little bit to recover if this is indeed a hamstring issue.