Graham Westley claimed Luke Freeman added to his value with two magnificent strikes to lift Stevenage off the foot of the table.
Bradford were leading 2-1 until Freeman struck twice in the second half to give his side their second win in four days.
Westley said: "The club will be delighted because Luke has put about B£5million on his transfer fee with that performance, so it is a really positive day for the long-term future of the club.
"He showed his class, drifting in from the right-hand side and proving a constant menace.
"I saw a post on Twitter that their left-back looked terrified - and he did. They were excellent finishes - one from a free-kick and the other an excellent piece of skill."
The win saw Stevenage climb above Notts County, the new back-markers, but Westley said: "I am not really worried about the table.
"I am more worried about winning games because that is what we have to keep doing."
Bradford led after only 11 minutes. James Hanson nodded down Carl McHugh's high ball from the left and winger Adam Reach volleyed past Chris Day from 15 yards for his first goal since joining on loan from Middlesbrough in January.
Stevenage hit back in the 23rd minute when Francois Zoko was allowed time to switch the ball on to his left foot and score from 12 yards for his 17th goal of the season.
Bradford regained the lead three minutes before half-time. Day parried Reach's low shot at full stretch, but Hanson was on hand to fire into the top right corner for his 11th goal of the campaign.
French defender Bira Dembele headed against Bradford's crossbar before Stevenage equalised for the second time, Freeman's powerful shot beating keeper Jon McLaughlin from 25 yards in the 64th minute.
Freeman then hit the 87th-minute winner when Jimmy Smith tapped a free-kick to him on the edge of the box.