Lincoln's Joe Gardner had a debut to forget as he was sent off as the Imps were held to a draw by Cambridge.
The Nottingham Forest teenager, on loan at Sincil Bank, was on the pitch for just four minutes before being shown a red card for a collision with James Brophy.
Michael Skubala's Imps missed the chance to close the gap in the League One play-off race after Freddie Draper's effort was cancelled out by James Gibbons.
Cambridge's on-loan Sunderland goalkeeper Nathan Bishop made a good save to keep out Draper's early effort.
But the striker made no mistake as he poked home a rebound in the 17th minute after another shot was blocked.
Kelland Watts did well to clear an effort off the U's line after a mix up at the back before Gibbons' deflected strike restored parity on the stroke of half-time.
After the break, Josh Stokes should have done better when he headed straight at Imps' stopper Zach Jeacock from point-blank range.
Lincoln's hopes of a late winner were dashed when Gardner was sent off.
The struggling U's nearly nicked it at the end when Watts saw his free header denied by Jeacock.
Match report supplied by PA Media.
