Alfie Mawson, Sam Saunders and Nico Yennaris all started as Wycombe Wanderers lost ground at the top of Sky Bet League Two after losing 3-2 at home to Oxford United.
Kemar Roofe and Danny Rose had the visitors 2-0 ahead after just 22 minutes.
Gareth Ainsworth's side pulled one back as Mawson's header was turned home at the back post by Paul Hayes just after the break.
Roofe extended the visitors advantage on the hour with his second of the match and despite an Aaron Holloway goal late on, United held on for the three points.
The defeat leaves The Chairboys four points above fourth placed Bury, but having played a game more than The Shakers.
Another seven Brentford players could be involved for their clubs today and tomorrow ahead of a full round of fixtures on Easter Monday.