Kgosi Ntlhe scored the only goal of the game as Barnet began their pre-season schedule with a hard-fought 1-0 defeat at home to Peterborough United.
The South African defender struck the decisive goal eight minutes into the second half, with the Bees unable to stretch Posh goalkeeper Bobby Olejnik after the break.
As expected, Martin Allen named two separate elevens for the game, with six trialists included in the Bees matchday squad.
Named in the starting XI were former Watford and QPR midfielder Gavin Mahon, ex-Leyton Orient and Brentford striker Charlie MacDonald and Will Antwi, formerly of Luton and Wycombe.
Peterborough boss Darren Ferguson opted for a strong starting XI, with summer signing Erhun Oztumer partnering Tyrone Barnett up front. Last season’s 33-goal top-scorer, Britt Assombalonga, started on the bench for the Posh.
The Bees had the first chance of note after 14 minutes when Luisma Villa planted a free-kick against the base of Olejnik’s left-hand post from 20 yards. From the rebound, new signing John Akinde shot against the far post.
Posh skipper Jack Payne had his side’s first effort on target in the 20th minute, dragging a low right-footed effort into the grasp of Graham Stack.
The Bees had threatened to get in behind the Peterborough back four on a couple of occasions and shortly before half-time, Keanu Marsh-Brown did exactly that, without finding the finish.
A perfectly-weighted pass from Curtis Weston found the winger on the edge of the area and having maintained his balance in spite of a push, Marsh-Brown could only slash his effort comfortably over from inside the penalty area.
The Bees made 11 changes at half-time – as promised – whilst United made nine; Olejnik and first-half substitute Tom Conlon the two to continue.
In a stop-start opening to the second period, it was the visitors who adapted better, taking the lead eight minutes after the restart.
The goal came when left-back Ntlhe held off the attentions of John Nurse and David Stephens to prod cutely beyond substitute goalkeeper Monty George and into the far bottom corner from six yards.
Luke Gambin tried his luck soon after, slashing just over the apex of crossbar and post via the aid of a deflection.
Following a spell of play, trialist Vinny Mukendi fashioned enough room to shoot but was unable to test Olejnik with a low right-footed effort from 18 yards.
Posh forward Conor Washington ought to have done better a couple of minutes later, prodding a meek effort wide after controlling an inch-perfect ball over the top.
Assombalonga – another half-time change – attempted a deft chip with eight minutes remaining but could only loft his effort onto the roof of George’s net.
Mukendi then went for something similarly audacious late on, directing a back-heeled effort towards the Posh goal following Sam Muggleton’s long throw in.
The Bees were unable to force an equaliser in scorching conditions at The Hive but had certainly contained League One Posh in a game which had always been about fitness rather than the result.
Barnet first half: Stack; Yiadom, Antwi (T), Saville (c), Johnson; Marsh-Brown, Mahon (T), Weston, Villa; Akinde & MacDonald (T).
Peterborough United first half: Olejnik; Ferdinand, Zakuani, Baldwin, Newell; Barnett, Anderson, Payne (c) (Conlon 31), Ajose; Oztumer & Vassell.
Barnet second half: George; Nurse, Nkumu (T), Stephens, Muggleton; Lowe, Vilhete (c), Sheriff (T), Gambin; Sykes & Mukendi (T).
Peterborough United second half: Olejnik; Drury, Bostwick, Brisley, Ntlhe; Mendez-Laing, Conlon (Santos 61), McCann (c), Taylor; Assombalonga & Washington.
Referee: Mr M Russell.