Hakim Ziyech was forced off in the second half of his Chelsea debut on Saturday afternoon, having seemingly picked up an ankle injury against Brighton & Hove Albion.
The 27-year-old played a key role in fellow new arrival Timo Werner scoring the first goal of the afternoon before Brighton hit back to claim a 1-1 draw courtesy of a late penalty from Pascal Gross.
Ziyech suffered a blow to his ankle in the early stages of the second period at the Amex Stadium, though, and was ultimately replaced in the 54th minute of the contest by Conor Gallagher.
The Morocco international could now be a doubt for Chelsea's Premier League opener on September 14, which also comes away to Brighton.
Kepa Arrizabalaga started for Frank Lampard's side despite the speculation surrounding his future, while there was also a spot in the middle of the park for N'Golo Kante.
Ziyech scored eight times and contributed 21 assists in 35 outings for Ajax last term.
Matt Law
