Cresswell, 28, has not featured in the Premier League for the Hammers this term, but did play the full 90 minutes in their 3-1 win over AFC Wimbledon in the EFL Cup on Tuesday night.
Pellegrini has branded Cresswell "a good player", but has suggested that the left-back will need to be patient as he is currently down the pecking order at the London Stadium.
"I spoke with the players before the cup game that I need to analyse the performances of all of them, in the Premier League, cup, training here every day," Pellegrini told reporters.
"Unfortunately for Cresswell he had a long injury and only played 45 minutes in the last game of pre-season. He did very well on Tuesday. He is a good player but others are also doing well. It is important to have a good squad and I can choose who deserves to play."
West Ham are back in Premier League action against Wolverhampton Wanderers this weekend.