Luton secured a 1-0 win at 10-man Cambridge to inflict a second home defeat of the week on their former manager Richard Money.Mark Cullen netted the winner nine minutes from time, stroking home the rebound after his own penalty was saved by Chris Dunn following Richard Tait's foul on Pelly Ruddock. Tom Naylor, signed on loan from Derby on Thursday, was shown a straight red card 54 minutes into his debut for a poor tackle on Jim Stevenson, forcing the U's to play most of the second half a man short. Ryan Donaldson fired wide and Tom Elliott struck a post as Cambridge enjoyed the better of the first period, before John Still's men dominated following the red card. Ruddock blasted an effort onto the crossbar from outside the box after 66 minutes, while Luke Wilkinson headed over from six yards out following Luke Guttridge's cross. Greg Taylor came closest to equalising for Cambridge, firing wide after Ryan Donaldson's corner fell to him in the last 10 minutes.