The damage was done in the first half as Rovers registered a comfortable victory against Southampton's Under-23s at Staplewood Training Centre.
The returning Dan Butterworth netted a brace on his comeback either side of Jack Vale's strike to put Rovers in command going into the half time break.
Home captain Callum Slattery did pull a goal back for The Saints midway through the second half, but that was to only be a consolation for the Hampshire-based outfit, with Rovers running out comfortable winners on the south coast.
Butterworth made his first appearance for a couple of months following a troublesome injury, whilst there was also a first start of the campaign for Ben Paton, who was also on the comeback trail following a long-term absence.
A youthful-looking squad included Under-18s regulars Flavian Boyomo, Dan Pike and Jake Garrett on the bench.
Rovers raced out of the blocks and went ahead inside the opening minute through Butterworth, who took just 14 seconds to make a scoring return to the team.
Vale robbed Pascal Kpohomou on the right-hand side before setting up Butterworth who confidenty stroked into the back of the net from an acute angle.
Southampton went in search of a quick response, with Slattery curling over from the edge of the box as Radhi Jaidi's side looked to hit back.
But it didn't take Rovers long to double their advantage soon after, with Vale getting in on the act with a smart finish from inside the box.
He got on the end of an Isaac Whitehall cross before taking a touch and emphatically slamming home a volley beyond Jack Bycroft.
That wasn't to be the only volley of the game, and Vale turned provider once more seven minutes later, with his cross perfect for Butterworth to superbly thump an effort into the corner with his unfavoured left foot.
That put Rovers in command at the interval, although Butterworth nearly completed his hat-trick just before the break, with his free kick parried by Bycroft only as far as Sam Burns, who blazed over the upright.
Butterworth's work was done as he was replaced at half time by Jalil Saadi, but the visitors kept the tempo high, and Stefan Mols prodded wide from close range after more great work from Vale up top.
Slattery made things a little nervy from the spot eight minutes after the break as he struck his penalty straight down the middle after he was fouled in the box by Hayden Carter.
Vale, Saadi and Sam Barnes all missed opportunities to add gloss to the scoreline, but Rovers managed to see the game out well and without any further scares and seal an excellent performance with the three points.
It's a second successive 3-1 away victory in a matter of days for Barr's boys, who defeated Crystal Palace by that scoreline in the Premier League Cup on Thursday afternoon.
The most recent result, in Premier League 2, moves the youngsters up to sixth in the league ahead of the trip to Liverpool's Under-23s this weekend.
Southampton Under-23s: Bycroft, Ramsay, Freeman (Hansen, 58), Kpohomouh (Morris, 72), O'Driscoll, Klarer, Slattery (c), Jankewitz, Norton (Brennan, 78), Defise, Mitchell.
Unused substitutes: Scott, Bellis.
Goal: Slattery pen, 53
Booked: Jankewitz, 30, Norton, 30, Slattery, 34
Rovers Under-23s: Hilton, Whitehall, Thompson, Paton, Carter, Barnes, Burns, White, Vale, Butterworth (Saadi, 46), Mols (c).
Unused substitutes: Dowling, Boyomo, Pike, Garrett.
Goals: Butterworth, 1,29, Vale, 22
Booked: Mols, 30.
Referee: Rick Hulme.