Rotherham United had top scorer Kieffer Moore sent off as they crashed to a third successive defeat in League One, at Bristol Rovers.
The Millers have gone seven league matches without a win and slipped to 13th in the table.
They went ahead in the second half against a Rovers side who had lost their previous six games, but couldn't hang on at the Memorial Stadium.
They were already trailing 2-1 when 13-goal Moore was shown a straight red card after an altercation with Lee Brown in the 79th minute.
After a goalless first half, the encounter came to life when Rotherham took the lead with their first attempt on target. Ryan Williams buried his 56th-minute shot after initially standing on the ball following Joe Newell's defence-splitting pass.
But their advantage lasted for just eight minutes as they only half-cleared a corner and Ellis Harrison prodded home when the ball came back into the box.
They fell behind in the 75th minute as Sercombe raced on to a looping ball into the area, controlled it and slotted it past Marek Rodak.
Four minutes later, Moore received his marching orders and now faces a three-match ban.
Michael Ihiekwe could have earned an unlikely draw for the Millers in the 89th minute but made a mess of his header from Newell's cross.
Bristol Rovers (4-3-3): Smith; Leadbitter, Lockyer, Sweeney, Brown; Sinclair, Partington (Lines 62), Clarke (Gaffney 62) ; Bodin, Harrison (Nichols 90), Sercombe. Subs not used: Slocombe, Broadbent, Broom, Telford.
Rotherham (4-4-1-1): Rodak; Cummings (Clarke-Harris 85), Ajayi, Ihiekwe, Mattock; Williams, Potter (Vaulks 22), Frecklington, Newell; Ball (Yates 85); Moore. Subs not used: O'Donnell, Wood, Towell, Forde.
Goals: Harrison 64, Sercombe 75 (Bristol Rovers); Williams 56 (Rotherham).
Referee: Brett Huxtable (Devon).
Attendance: 7,531 (226).