City are all-but guaranteed a place in the final at Wembley after thrashing the Hammers at the Etihad Stadium two weeks ago and, although Manuel Pellegrini will rest some key players, keeping a winning mentality remains important for the manager and his players.
They go into the Upton Park game on a 17-game unbeaten run in all competitions, dating back to defeat at Sunderland in November, and 15 of those matches have ended in victory.
Pablo Zabaleta, who is one of the players likely to get a midweek rest, said: "It doesn't matter about the first leg.
"We have to go into that game thinking it's a new game, even though we have six goals.
"We need to try and win it, like we are doing in other games at the moment. We are winning games and working hard.
"West Ham are in a tough moment, they are at home and will want to win it. So we need to take it seriously and we will."
Pellegrini will take the chance to give his regular starters a rest but, such is the depth of his squad, a strong starting XI is almost assured and he wants the squad to continue their fine recent form.
He said: "We have to play on Tuesday. The semi-final is not finished.
"Of course we have made an important step (towards the final) but we must see which players will play and the way we will do it."
Watch live coverage of the Capital One Cup semi-final second leg clash between West Ham and Manchester City on Sky Sports 1 on Tuesday from 7.30pm.