The 27-year-old Irishman returned for pre-season training having shed more than a stone in weight in an effort to persuade his new manager that he was worth a place.
Bruce has been pleased with what he has seen from Reid, but admits he faces a major fight with Kieran Richardson for a place on the left side of midfield with summer signings Lee Cattermole and Lorik Cana having started impressively in the middle.
The manager said: "Fair play to Andy, he has gone about it and thought, 'I am going to do everythhing I possibly can physically'.
"There's never been any question about Andy Reid's ability, the big question mark has been physical, and for him to do what he has done - shed nine kilos and 22mm of body fat - is quite an unbelievable turn-around in six, seven, eight weeks.
"He has taken it upon himelf, the penny has dropped with him, that to play at this level in the Premier League, you have to be physicially at your peak. The only problem I have got, of course, is that Kieran Richardson in his position is an excellent player too who has had a decent start to the season as well."