The pressure is mounting on Pellegrini after a seven-match winless streak saw them slip towards the relegation zone.
With a trip to Chelsea followed by fixtures against Wolves and Arsenal, it is a situation that could get a lot worse before it gets better.
However, Pellegrini has shrugged off speculation about his position, saying: “We never talk about the future.
“You must be clear, it is game by game. It is the same question asked when we were winning. Football changes every game so we are working to beat Chelsea and improve. I always think about the present, never the future.”
Back-up goalkeeper Roberto has taken much of the flak for West Ham’s poor run and was badly at fault again during Saturday’s 3-2 home defeat by Tottenham.
Regular keeper Lukasz Fabianski is still injured, and likely to be sidelined for another month, but Pellegrini gave no guarantee that he will keep faith with Roberto.
Should he axe the 33-year-old Spaniard then third-choice keeper David Martin, signed on a free transfer from Millwall in the summer, will be pressed into action at Stamford Bridge.
“Of course I am concerned, but it is not just about the goalkeeper,” added Pellegrini.
“Every time you decide your starting XI you have the complete week to work with them, and the technical staff, about positives and negative things.
“We will see. Our best starting XI, in all the positions, will start the next game.
“Of course it’s not a comfortable position (for Roberto). He knows exactly about his performance, he has a career behind him, he has been a very good player in big teams so of course he cannot be happy in the moment, but it is what has happened and he must try to improve.”
Jack Wilshere and Manuel Lanzini are still out injured for the trip to west London.