Gunners captain Vermaelen was left on the bench for the 2-0 UEFA Champions League victory at Bayern Munich, while Poland goalkeeper Szczesny was rested for the game.
Wenger says both players have had a positive reaction since then, as the Gunners slipped out of the competition on the away goals rule after a 3-3 aggregate draw, and will play vital roles during the Premier League run-in.
"They are two outstanding players who are part of our squad," Wenger said.
"They have played so many games until now. Their position is very important in the squad.
"All the players are in the same position: nobody is guaranteed a place in the team. When you go into this job, you know you have competition.
"Everybody faces the same competition and the players who have come in have been on the bench for a long, long time. They all have the same problem. The job of being a top-level competitor is to deal with that.
"Every position is up for grabs. You have to face it like that. The last game decides the next one."
Wenger underlined his support for both Szczesny and Vermaelen, and believes they both have a big future in north London.
"Who gave Wojciech a chance from nowhere in the youth teams? It was me because I rate him highly and have a big respect for what he has done," he said.
"But we all have ups and down physically and mentally and he has played many, many games this season. Maybe I should have rested him in the cup games but I did not do that. It is normal that you have ups and downs. He is a young goalkeeper.
"Thomas Vermaelen has played many games in many positions and is a very important player in our squad. They know there might be rotation with the three centre-backs - Vermaelen, Koscielny and Mertesacker."