Robbie Neilson suspects ref Kevin Clancy was influenced by the Celtic Park crowd in sending off two Hearts players on Sunday.
The official dismissed both Alex Cochrane and Toby Sibbick for second bookable offences during the Jambos' 2-0 defeat in Glasgow's east end. Cochrane was sent packing for catching Callum McGregor and Sibbick for pushing Liel Abada as he raced forward.
A second-string Hearts had made Celtic work and were chasing a second-half equaliser after Kyogo Furuhashi put the hosts ahead in the early minutes. But Neilson reckons they were robbed of the chance to claim a point and was particularly frustrated by Cochrane's dismissal. The Tynecastle boss claimed the roar of the home crowd may have had an effect on Clancy's decision-making. He told BBC Sportsound: “Until the referee sends two of our players off, we’re still in the game and in a good position, but once that happens, it makes it very difficult.