The 27-year-old has not played for England since landing a match-winning drop-goal in the 2003 World Cup final.
Wilkinson's latest problem - a lacerated kidney - meant 12 weeks on the sidelines, although he has been retained in a 29-man England squad preparing for the world champions' RBS 6 Nations appointment with Scotland on Saturday week.
Realistically, Wilkinson might not feature for England until mid-Six Nations, although Ashton termed his contribution at a three-week Twickenham training camp this week as "staggering."
Newcastle have named Wilkinson among nine substitutes - the bench will be reduced to the regulation seven tomorrow - with every chance of him gaining a run-out against Tigers.
Ashton said: "If Jonny is back and has played a couple of games, it will be about form.
"And recent history shows that when he comes back from injury, he plays better than he was in the game before he got injured. It is almost unbelievable.
"But it is because he works incredibly hard. He is like Tiger Woods.
"Tiger Woods has got talent, but he works harder than anybody else. Jonny Wilkinson has got talent, but he also works harder than anybody else.
"He (Wilkinson) is a lot more mature now, and I think his understanding and knowledge of the game has developed during all of his time out injured.
"He brings a wealth of experience, and if you match that with his skill set, you have a world-class player on your hands.
"He has been staggering in training this week. I hope he will be back in the team as soon as possible."
Newcastle rugby director John Fletcher will make a final decision on Wilkinson for this weekend after speaking with him on Friday.
Fletcher said: "In terms of his injury and his fitness there is not a problem. It is just a case of whether he has done enough collision and contact work to be thrown into a game."