The nine-year-old, owned by Diamond Racing, gave trainer Sam Thomas the biggest victory of his burgeoning training career when beating Highland Hunter in the extended three-and-three-quarter-mile Grade Three marathon at Chepstow.
Iwilldoit relished the testing conditions in a race where just five of the 20 starters finished.
However, the nine-length success under Stan Sheppard came at a price, as his exertions took their toll and he has not run since.
Though the prognosis is favourable, Thomas feels he may need a little more time to recover from the undisclosed injury.
He said: "He had a bit of a niggle after that race. We have just taken our time with him, and he is in full work, and whether we get him back at 100 per cent peak fitness for the Welsh National this time, I'm not sure.
"There are lots of other targets for him later in the season.
"The Welsh National may come a bit soon, but we are aiming him for that currently and if it doesn't work out, then it doesn't work out. It is not the end of the world. He still has no miles on the clock, so we will have to see."
Thomas, who hit the heights as a jockey with his fruitful association with Denman, feels Iwilldoit can develop into a top staying handicapper.
He added: "He potentially could be a Grand National horse. I will have to have that conversation with the owners and see what they want to do. He certainly stays now and it would be nice to have a runner in a race like that."
Good Risk At All, who won a valuable Ascot handicap hurdle in February and who has only failed to be out of the first two in eight starts for the Lisvane, South Glamorgan trainer - when sixth in the Grade One Mersey Novices' Hurdle on his final start last season - is set to make his return at Carlisle on Sunday.
"We are looking to get him going at Carlisle. He is in good form and hopefully we still have got a bit of wiggle room with his handicap," said Thomas.
"There is a nice, £100,000 handicap hurdle over two and a half miles at Ascot before Christmas that we are likely to aim him at if we can.
"We might more than likely go over fences if all goes well over hurdles early doors. We maybe pursue that avenue, but he jumps very well and is in good form.
"We will see how he fares over hurdles first. He has always been a brilliant jumper and we're looking forward to getting him going again."
Meanwhile, Skytastic, who won a pair of bumpers, and a maiden and novice hurdle on his first four starts for the yard last term before having his colours lowered in the Sefton Novices' Hurdle, is being primed to make his chasing debut.
Thomas added: "He's good to go. We will make an entry for him at Newbury next week over fences and also at Warwick in a novice chase.
"He has been schooling very well and we're very excited that he has grown a lot over the summer.
"Skytastic is 17-hands-plus and is a monster. He has got no miles on the clock and hasn't had a lot of experience. We are looking after him and it is baby steps."