City were subdued in a goalless draw at Swansea City last weekend, as the gap between them and third-placed Chelsea got reduced to four points.
Zabaleta believes that manager Roberto Mancini is yet to decide on his starting XI for the Wembley showpiece and could be persuaded by a strong individual performance against the Baggies tonight.
He told The Mirror: "We will all be playing for places at Wembley. Every single player will want to show the manager that they want to play in that game.
"We want to keep winning to make sure we get second place. Then we can turn our focus to Wembley. Hopefully winning will give us momentum for such an important game. Winning gives you confidence and makes you stronger.
"It's important for the club to keep winning trophies. The main target for the team was to retain the title which was difficult but winning the FA Cup is always important because it is a special competition."
The Argentine full-back has made 40 appearances in all competitions for City so far this season.