Eric Kinder felt his side's sloppy start lead to their downfall as the Under-21s lost their first match of the season 3-1 away to Middlesbrough.
Boro were much the better team in the first half at the Riverside as England youth international Bradley Fewster profited from poor play to give the home side a 2-0 lead.
Despite Thomas McAloon adding a third, Rovers improved greatly after the break, substitute Sam Joel's first goal at that Under-21 level the reward for their endeavours.
"I'm disappointed with the start," said Kinder. "I had a go at them in the warm-up because the warm-up wasn't right, our passing wasn't right, we were slow at everything we did.
"I told them that a warm-up is a gauge for the start of the game and it was proved right, it was a very poor start.
"Then it was unfortunate for David that his mistake leaves us with a lot to do at the start of the second half.
"The next goal wins the game, we know that at 2-0. If we get it then it is game on but if they get it then it is probably dead and buried.
"We get one back, which is what we deserved, it is just a shame we couldn't turn one of those half chances into another goal late on.
"But to be fair to Middlesbrough they were better than us tonight."
The Under-21s are back in action this Friday night when they face Stoke City at Leigh Sports Village. Kick-off 7.00pm.
Season ticket holders can see the match for free on production of their season ticket cards, whilst non-season ticket holders can also gain free admission by registering at www.leighsportsvillage.com/rovers