Haskell made his return from a toe injury as a second-half substitute, but was forced off almost immediately.
Haskell made his return from a toe injury as a second-half substitute, but was forced off almost immediately after hurting himself in a tackle on Leicester's Freddie Burns.
Wasps rugby director Dai Young gave a positive initial prognosis, but admitted Haskell faces a race against time to be fit for next Saturday's key European Champions Cup clash with Toulouse.
"He is totally fine now," Young said. "He had a real big hit and had a bang on the head, so he has got to go through the protocols.
"It was the best 36-second comeback ever, so he is having a bit of a ribbing off the boys, but all jokes aside, thankfully he is OK. He took a nasty bang to the head.
"It's a six-day protocol, so he has got to tick all the boxes. It's certainly touch and go (for the Toulouse game). It's certainly going to be tight."
Wasps were 19-0 up before half time following tries by Christian Wade, Tommy Taylor and Dan Robson, but Leicester made a game of it in the second half in their first match since Richard Cockerill's departure.
Cockerill was sacked as rugby director last Monday, with head coach Aaron Mauger stepping in on an interim basis, and the New Zealander was encouraged by the visitors' second-half fightback.
Centre Peter Betham touched down, Owen Williams kicked two penalties and Burns contributed a penalty and a conversion.
But Jimmy Gopperth landed a late penalty, to go with two earlier conversions, to keep Wasps in front, after Leicester's England prop Dan Cole had been yellow-carded.
"I don't think you could ever question the character of our guys," Mauger said.
"We talked about playing for each other before we got on the bus. I was really proud of the way the guys responded in the second half."
Wasps move back above defending champions Saracens, who drew 13-13 with Exeter on Saturday, while Leicester return to fifth place.
Wasps made three changes from their win over Newcastle, with Gopperth and Kurtley Beale among those coming in, while Haskell took his place on the replacements' bench.
In the absence of the injured Manu Tuilagi, Betham and Matt Smith teamed up in midfield for Leicester, with Tom Brady slotting in for Betham on the wing.
Buoyed by a 10-game unbeaten run at the Ricoh Arena, Wasps took charge of the match with two tries in the opening 10 minutes.
Wade poached a converted try before Taylor was driven over after James Gaskell won possession from a line-out.
Wasps' third try followed a fine move started by Welsh Six Nations hopeful Thomas Young, who ran from his own half before finding Josh Bassett, who allowed Robson to finish from close in.
Gopperth added the conversion to make it 19-0 in the 35th minute and Williams's penalty response for Leicester appeared unlikely to provide the foundation for much.
Williams was forced off by injury after landing a second penalty early in the second period, but a fantastic show of skill by Brady brought Leicester back in the match.
It allowed Leicester to set up a platform that enabled Betham to touch down, referee Craig Maxwell-Keys awarding the score after consulting television match official Stuart Terheege.
After Burns kicked the conversion, Haskell made his long-awaited but short-lived return.
A Burns penalty took the away side to within striking distance, but after Cole's sin-binning, Gopperth made sure Wasps had the final say.