Needing 21 runs of the last over, Balaji was hit for four consecutive boundaries by James Franklin and then Ambati Rayudu finished off the run chase with a six off the last ball to end Mumbai's three-match losing streak.
But Gambhir expressed confidence that Balaji will make a strong comeback in their eliminator against the same opponents on Wednesday at the Wankhede Stadium.
"It happens in cricket. Bala tried his best. This is what happens in T20 cricket, it's just one of those bad days.
Sometimes, you have to bowl to your field, sometimes you have to bowl smartly. Bala will comeback strongly," Gambhir said after the match.
Mumbai Indians captain Sachin Tendulkar said he was happy to get back to the winning momentum ahead of the play-offs, especially after a hat-trick of defeats.
"It was a wonderful match. Our team batted well, great finish by Rayudu and Franklin. It was important to regain our momentum," he said.
"Anything is possible in this game, it's a tricky game, if the bowler doesn't get it right and the batsman is lucky, that''s what can happen."
Man-of-the-match Franklin, who played a match-winning innings of 23-ball unbeaten 45, agreed with his skipper and said it was important to return to winning momentum going into the play-offs.
"We were lucky to get some edges, and Rayudu finished off superbly. They gave some room in the end and it gave us an opportunity to free up. It was important for us to get some momentum," the Kiwi left-hander said.