Brentford's revival came to an end with their first defeat in Cambridge for nine years.
Brentford made an enforced change, Theobald slotting in for the suspended Powell.
It seems to be rosy in the Bees camp after five minutes, an unmarked Burgess header beating Perez to give The Bees a great start.
After controlling most of the first half it was no suprise Brentford went into the break ahead.
The Bees took the game to Cambridge, the first fifteen minutes being all Brentford but a canny substitution from U's manager John Taylor swung the game back to Amber and Black, Wanless powering a header home to give Cambridge a deserved equaliser.
The 599 Brentford fans went home disappointed, it looked like they might leave The Abbey Stadium with a point, Chillingworth raced past the two Bees centre backs to give Cambridge all three points and their first win since October.