Rojo hobbled off after 55 minutes played in the 3-2 win over the Gunners and was replaced by Timothy Fosu-Mensah.
The injury came as a blow as Rojo had only just returned from a dislocated shoulder. However, van Gaal insisted that the defender could be back sooner than expected.
Speaking to reporters, van Gaal said: “It was a kick. A lot of players receive kicks and they can play the next match.”
The club has had to contend with a number of injuries in recent weeks and, although players such as Marcus Rashford and Guillermo Varela have ably made the step up, it will be good to see United’s more established stars back on the pitch.