Aston Villa beat Nottingham Forest 1-0 yesterday at the City Ground.
Bjarnason was picked to play in midfield against Forest yesterday, and the Icelandic international impressed.
Bjarnason has generally played at wing-back for Villa, but he was moved into a more central role yesterday.
Bruce now admits that he took a risk by picking the 29-year-old to play in a new role and it was a gamble that paid off, as Villa picked up a 1-0 victory.
“I'm really pleased for him,” Bruce said.
“It was an experiment to see if he could play there and he proved he can.
“I was delighted for him because it's not gone as well for him as we'd all have liked since he arrived.
“A performance like that will do him the world of good.”
Bjarnason has actually been linked with a move away from Villa recently, but he may well have convinced Bruce that he still has a part to play with his showing yesterday.
Villa picked up their 1-0 victory thanks to a goal from Scott Hogan, with the striker heading home from close range to seal the three points.
Bruce’s side are now in fourth place in the Championship table, and they are only five points away from the automatic promotion spots.
The Villans are next in action against struggling Barnsley in a week’s time.