Stevenson produced a two-footed lunge on Hibs skipper James McPake at Tynecastle and despite not even receiving a booking for the incident, Fenlon was furious with the Jambos man at the after-match.
"It's a shocking tackle. He had a look first before he left the ground," Fenlon said.
"We're disappointed with that. He has a bad gash, James. There could have been a bit of damage there, but he's not too bad.
"The ref has had a bit of a stinker there by letting that one go. For me it's a red-card tackle.
"I thought the ref did quite well but not to see that one was pretty poor.
"James is the kind of guy who is not going to make a fuss over nothing and straight away he said to the ref it was a two-footed lunge.
"Everyone saw that but him. He's got quite a nasty cut on his leg.
"But it's over and done with now and we're just happy to come here and still be unbeaten in derby games this season."