Nothing like a bit of hydrotherapy to speed along a muscle injury, which, by all indications (including his call-up to the Brazilian national team) is just a minor problem for Willian.
While Willian believes it's "nothing serious" and that he "probably will return to work in the field in the coming days", that still puts his recovery timeline beyond this weekend's matchup against Arsenal. Plus, with hamstrings, you can never be too careful.
There's no word yet on Pedro's status, but if he's also not able to go, we might be scrambling to fill the right wing spot on Saturday. I would imagine Ramires would be the front-runner to get the start, but perhaps Mourinho will roll the dice and go with one of the youngsters Kenedy or Bertrand Traoré.
In any case, at least it's good news that Willian's injury is not too serious.