The young Black Cats handed starts to several first-team players in Monday’s fixture, with goalkeeper Thorben Hoffmann, Elliot Embleton, Arbenit Xhemajli, Danny Batth and Leon Dajaku all playing 90 minutes.
But, despite a bright start, two goals from Burnley defender Owen Dodgson gave the hosts a surprising victory in the Premier League 2, Division 2, clash.
“I thought in the first half we created the better chances and probably should have been leading by half time,” Proctor told the Echo after the game.
“In the second half I thought we didn’t really come out with the same intensity and didn’t match their workrate which is a problem at any level of football.
“Ultimately that’s what cost us in the second half.”
This isn’t the first time senior players have played for the under-23 side in recent weeks, after Patrick Roberts asked to play a fixture against Stoke last month.
In fact, Batth, 31, was the only overage player, with the central defender stepping up his rehab following an ankle injury.
When asked about first-team players featuring for the under-23 side, Proctor added: “The thinking was that they needed minutes.
“Obviously Danny Batth is just coming back from an injury and in terms of his rehab it was great for him to get 90 minutes.
“Some of the lads needed minutes because they haven’t played recently and it was an opportunity to stake a claim.
“It was a top up for them and I think they were all more than happy to play.
“It probably goes the same for everyone, in the first half we were ok, second half not so good.”
Sunderland have also been looking at a couple of tralisists in recent weeks, with defender Ugonna Emenike, 18, signing a professional deal with the club.
Winger Michaeal Spellman, who has played for Northern League side Chester Le Street, once again played for the young Black Cats against Burnley, yet full-back Sean Wilson has returned to Liverpool following a trial period.