Rosicky had just come back from an injury lay-off, and Wenger revealed his second-half substitution was pre-planned.
He said: "Tomas has not played for six months and we were cautious with him.
"We decided before the game to play for 45 minutes and see how he got on. He is a bit tight, muscular, but no [new] injury.
"We will see how we recovers now for Saturday."