Gary Waddock was at a loss to explain Wycombe's slow start at Southend, something which has dogged them this season.
The Shrimpers scored the only goal in the seventh minute when Kevan Hurst's corner from the left was headed goalwards by Ryan Cresswell and although Matt Spring cleared off the line, Britt Assombalonga nodded the ball in from eight yards for his second goal of the season.
"The first five minutes cost us when we started slowly again," said Waddock. "Southend scored and we were chasing the game for the remainder of the half.
"We changed things around to try and get the ball into the forwards' feet because their centre-halves were winning everything in the air.
"We've just had a discussion about it. Everyone was up for it but they just didn't perform. I can't put my finger on it.
"We tried to change things around but it didn't happen for us. We had more possession in the second half but we didn't work their goalkeeper enough."