Everton midfielder Jean-Philippe Gbamin is facing a two-month lay-off after picking up a thigh injury.
Ivory Coast international Gbamin was signed from Mainz as a reported £25million replacement for Idrissa Gueye during the close season and featured in his new side's opening two Premier League matches.
A right quadriceps injury ruled the 23-year-old out of Friday's 2-0 loss to Aston Villa, however, and Everton has confirmed he will miss "at least eight weeks".
Gbamin will undergo further tests this week, with leading experts being drafted in from around Europe to ensure the swiftest possible return.
"It's a tough moment for him of course, and we are here to support him as much as we can because it's not an easy moment," said Marco Silva. "But it's part of the football, it can happen.
"He had his debut in the first game against Crystal Palace, everything was so fast for him after coming in at the end of the market. He played the whole match against Watford as well.
"The player knows what's happened now, and it's up to us to put him in the best condition as fast as we can."
Fellow new recruit Fabian Delph is still on the comeback trail after injuring his groin in pre-season, leaving boss Silva short of options in holding midfield.
Everton faces Lincoln City in the EFL Cup second round on Wednesday and Wolves in the Premier League four days later, before a two-week break for international action.
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