Isak has struggled with injury problems all season, specifically a toe injury, but is now fully fit.
The Swedish forward netted in a 3-1 win away from home against high flying Nottingham Forest.
Post-game, Barnes told Premier League Productions: "You could see it was just a matter of time for Alexander Isak once he scored that he would go on a run. We are a much better side when he's firing. It's great for him to get on the scoresheet again.
"I want to start games. You never want to be on the bench, but when you are, you do everything you can when you come onto the pitch to get back into the team. I can do what I do from the bench from the beginning.
"The league table is so tight. It's nice to move up a few places, but the international break comes at the wrong time for us really because we're on a good run."