Dean Wilkins believes some of his Albion under-19s have allowed the influx of new players at the club to adversely affect their performances.
First team boss Steve Coppell has signed Simon Rodger, Dean Blackwell, Ben Roberts and Dave Beasant, plus the now departed Steve Sidwell and Daniel Webb, as Albion battle against relegation.
After the 3-1 defeat against Leyton Orient in the Youth Alliance, Wilkins said: "It has been a difficult time at first team level and the gaffer has understandably brought in experienced players to help.
"Everyone likes to see progression but because of the new players coming in, opportunities up a level have become more limited. There is a gridlock and when some players don't get reserve games they let it play on their minds during matches.
"It's not a big problem but it shouldn't be a problem at all. Those affected should not allow it to happen."
Mark Windsor scored the consolation goal and Albion hope to put things right against Wycombe at Sussex University on Saturday (11am).
Meanwhile, Albion under-17s hope to increase their lead at the top of the Youth Alliance at Wycombe on Saturday.
The Seagulls took over the top spot thanks to a 3-1 win over Colchester at Lancing College.
Jake Robinson fired two goals to bring his season's tally to 14 in ten games. Matt Stillman netted the other goal.
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