N'Golo Kante has left Chelsea's tour of Japan to undergo rehabilitation on an issue stemming from the knee injury he suffered late last season.
Chelsea confirmed Kante's departure from their Saitama base less than 48 hours after the friendly loss to Kawasaki Frontale in Yokohama.
The midfielder missed multiple matches for club and country throughout May and June – though he started the UEFA Europa League final – and has failed to feature in pre-season so far.
Chelsea open their Premier League campaign against Manchester United on August 12.
"N'Golo Kante has travelled back to the UK to continue his rehabilitation for an injury connected to the knee problem he sustained at the end of last season, " the club confirmed on Twitter.
Speaking before the journey to Japan, head coach Frank Lampard said of Kante: "[He's] still feeling the effects of his injury from the end of last season, which we know with the Europa League final.
"It's not a problem, we know he's a fit boy, we know he's got a great attitude."
Kante's potential absence at the start of the 2019-20 season could generate more opportunities for Mason Mount, who played over an hour against Kawasaki Frontale.
The young midfielder idolised Frank Lampard growing up and hopes years spent modelling his game on the club legend will lead to a Stamford Bridge breakthrough.
"Being at Chelsea, and being a midfielder, the thing I took from him was how he got into the final third to score goals and make assists," Mount told reporters.
"He was the one I always looked up to as a role model, watching his game, trying to learn from him and working first hand with him.
"There's no one better to learn from and speak to day in, day out."
Chelsea's next pre-season outing is against Barcelona on Tuesday.