Gainsborough could not manage to extend their unbeaten run as Bradford PA claimed all three points thanks to a first half strike.
Chib Chilaka poked home from a corner as Avenue took advantage of their dominance in the first period.
Darryn Stamp came closest in the second half for the Blues when he had a header cleared off the line.
There was more bad injury news by the end of the game as Charlie Binns lasted four minutes off the bench before he limped off with an ankle injury he picked up when putting Craig Reid through on goal.
One change was made to the Trinity side that was victorious last time out away at Corby. The injury picked by Marc Newsham early on in the win kept him out, with midfielder Jamie Yates starting in his place.
The visit of Bradford was the first of three straight home games for the Blues, with Curzon Ashton visiting next Saturday and Brackley on Tuesday week.
Trinity started slowly in this one and could have been behind within two minutes when Lamin Colley climbed highest at the far post to head over a free kick.
Colley came close not long after when he managed to beat Jan Budtz to the ball with the attempted lob being cleared by Dom Roma.
Two minutes later, Luke Dean had a go from range was not cleanly executed but forced Budtz to back pedal and tip it over the bar.
From the corner the visitors took the lead.
The ball was not cleared by the defence and Chib Chilaka took advantage and fired Avenue into the lead.
The visitors could of gone in further ahead as from another corner Ryan Qualter turned the ball inches wide.
On the stroke of half time Colley should have doubled the lead when he tackled Budtz on the edge of the box, with the ball spinning into a shooting position but Budtz managed to save the strike.
The Blues were quickly on the front foot after the break with Jake Picton hitting a thunderous drive from the edge of the box that had to be parried out for a corner.
The visitors were still a threat though on the break and reminded the Blues of that when Colley forced Budtz into a stop at his near post.
Darryn Stamp came on just before the hour mark and Trinity were a bigger threat instantly going forward.
The veteran came closest for Gainsborough when he met a Yates cross. The header beat the keeper but not the man on the line who came out of nowhere to somehow clear over his own crossbar.
It looked to be the start of something for the home side as a minute later Craig Reid forced a save from Jon Stewart with a firm drive.
Bradford matched everything else that Trinity could throw at them and fashioned some opportunities of their own on the break with Chilaka and Craig King forcing Budtz into saves.
Reid had another chance to get the equaliser later on when he ran onto a through ball and fired across goal from the corner of the box flashing past a stranded Stewart in the Avenue goal.
Gainsborough Trinity: Budtz, Roma, Lacey, Wildin, D’Laryea, Picton, Russell, Davis (Stamp 58), Richards (Binns 82 (Bemrose 86), Reid, Yates. Subs (not used): Karkach, Hedge.
Bradford Park Avenue: Stewart, Scott (Marshall 63), Mather, Turner, Qualter, Priestley, King, Dean, Chilake, Colley, Patterson. Subs (not used): Potts, St Juste, Ainge, Tyrell.
Goalscorers: Chilaka 19.
Bookings: Turner, Qualter, Dean.
Referee: Mr J Hull. Assistants: Mr A Cawtherley, Mr A Smith.