Joelinton grabbed his second goal since joining for £40m, and first for 142 days, since August.
They claimed a home tie to Oxford United, scoring three goals in nine first half minutes, including Miguel Almiron's fourth of the season.
Bruce said: “We look forward to the next round! Joelinton is young and we are all relieved for him.
“There is an expectation on him. A transfer fee, a burden. Sometimes that becomes difficult.
“He wants to do well. He has wanted to do better than he has done and my job is to keep pushing him along. I was determined to leave him on to get his goal. That is the pleasing bit of the night.
“Let's hope he now gets the confidence every striker needs."
Joelinton ran to Bruce after his 82 minute goal to thank his manager, and Bruce, who's suffering a bad back, joked: “I was worried he was going to jump on me. He was shouting something in Portuguese. He has a big heart."
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