The USMNT star has not played for Chelsea since a 2-2 draw against Sheffield United on August 31
Chelsea manager Frank Lampard has explained that his continued omission of Christian Pulisic is simply down to other players being preferred at the moment.
"I have a squad to pick from, he played before that in a few games," Lampard said of Pulisic.
"Willian has come back and looked sharp and good. I decided to go with Mason today. We needed to stay strong and play Mason high up the pitch. That's my choices to make.
"[Pulisic] will get ample opportunities. He is a young player as well. Everyone talks about Mason, Tammy [Abraham] and Fikayo [Tomori] but he is young and younger than some of them so his chances will come."
It has been suggested that Pulisic is struggling to adjust to his new surroundings in London and the Premier League, but Lampard has denied those claims.
"It is not the case [that he hasn't settled in]," Lampard said. "There's Pedro, Ross Barkley and [Michy] Batshuayi on the bench.
"[Batshuayi] deserves more minutes from the way he is training, those are unfortunate choices I have to make."
Overall, Pulisic has tallied one assist in four Premier League appearances this season, three of which have been starts.
However, the winger has not played at all for Chelsea since a 2-2 draw against Sheffield United on August 31.
That could change on Wednesday, however, as the Blues welcome League Two side Grimsby Town to Stamford Bridge in a Carabao Cup fixture.