Muhamed Besic and Kevin Mirallas are set to miss Everton's crunch League Cup semi-final second leg against Manchester City on Wednesday through injury.
Besic played just 11 minutes of his side's 2-1 Premier League loss to Swansea City before being replaced by Tom Cleverley after suffering a hamstring injury.
Mirallas did not last much longer, being forced off with a knee injury after just 28 minutes.
Everton will take a 2-1 lead to the Etihad Stadium after Romelu Lukaku's 78th-minute winner in the first leg, but Roberto Martinez's side's hopes of progression have not been helped by Sunday's injury toll.
"It's hard to tell [the seriousness of both injuries]," he explained after the game.
"Muhamed Besic injured his left hamstring - the opposite leg to the problem he had recently.
"We will also assess Kevin Mirallas, who injured the tendon in his right leg around the knee.
"I don't expect them to be fit for Wednesday and I expect a bit of a period where they will be unavailable. It is a real shame because both players gave us a really refreshing look and reached good levels at this stage of the season."
Martinez was at least thankful to have been able to rest captain Phil Jagielka following his return from injury.
"We have five games in 13 days," he added.
"Phil Jagielka has been out for a long, long time and then he came back last week and played three games in seven days.
"Medically, it was the right thing to give him a bit of recovery time and make sure we used the squad. The squad is ready to cope with players missing and, clearly, Jagielka will be refreshed for what is ahead."
