Alex Morris has urged his players not to waste their opportunities to stake a claim for a starting spot.
The manager made seven changes, including handing out five full debuts, for the Carabao Cup tie at Grimsby Town in midweek.
It was a disappointing evening, with the home side running out 4-0 winners and Morris making five substitutions as he tried to change the momentum of the game.
Now the boss has made it clear to his men that they must take their chances to impress.
Morris said: "At any club, particularly at our level, squad depth is never as great as you’d see in the top two divisions.
"You’ll have players you think would fall into your best 11, and then it’s up to the others who don’t fall into that category to quickly get in a position where they are considered in that bracket, that’s the nature of football.
"The younger boys coming through, they are looking to make small steps and forge a career. But for the more senior pros, they need to make an impression and it is more urgent. Tuesday was an opportunity they didn’t take with both hands."
He added: "Footballers have to be mentally tough and have plenty of fortitude, and it’s the same with the staff.
"We have to swiftly move on. It’s a tough industry and if you’re not willing to take the knocks it’s not worth you being involved, because it is full of peaks and dips."