But the Falcons medical team have given the 28-year-old fly-half the green light to feature in the shoot-out for a place in the semi-finals of the Anglo-Welsh Cup.
And in another timely lift for Newcastle, director of rugby John Fletcher revealed Toby Flood is also available after recovering from his ankle problem.
Fletcher said: "We definitely have Jonny and Toby back fit for Saturday and both will start the game.
"Both Toby and Jonny are fine. Jonny was very close for last weekend's Premiership game at Wasps after his ankle injury.
"Toby has fully recovered from his own ankle problem and the other injury to a delicate area which we won't mention!"
New Zealand prop Carl Hayman arrived in Newcastle this week to begin his three-year contract and Fletcher revealed the front-row colossus could also figure against Wasps.
"Carl trained with us this morning and again in the afternoon," he said.
"But he has had a long journey this week and a big move, so we'll have to sit down with him and see if this weekend is right to get him involved."