Dual Paddy Power Stayers' Hurdle winner Flooring Porter won one of his five novice chase starts last season but was last seen powering to victory under a prominent ride in the Guinness Kerry National at Listowel on September 25.
However, he is now unlikely to be seen for the remainder of the campaign according to his trainer.
Cromwell said in his William Hill blog on Friday: “Unfortunately, it looks as though Flooring Porter will be out for the season.
"He’s picked up an injury and his return date suggests he’ll most likely miss the rest of this campaign.
"The timing of it means it’s unlikely he will be able to make it back for the big meetings in the spring, so it’s in the best interest of the horse to give him all the time he needs to recover.
"He’s been a real star for us so far so it’s really unfortunate that we won’t be able to see him again this term.
"He’s given connections some amazing days up until now and hopefully there will be many more of those to come.”
Cromwell also provided an update on two other leading hopes for the yard this season, Limerick Lace and Inothewayurthinkin.
“Our star mare last season was Limerick Lace and she finished off her campaign with a valiant effort in the Grand National," he said. "She came out of the race, and the season as a whole, well and really earned her summer break.
“She’s trained well since she came back but she definitely wants some rain, which we haven’t really had yet this season. Her main target will be the John Durkan at Punchestown later this month, but she also holds an entry in the Betfair Chase at Haydock, although connections already have Corbetts Cross entered there. We have her in both just in case, we’ll see how things unfold and where the rain falls.
“The Mares’ Chase at the Cheltenham Festival will be her main target for the season, then with all being well she could potentially go to the Grand National again.
“Another we have entered in the John Durkan is Inothewayurthinkin, and he’s also another that will need a bit of rain before he gets a run. He’s likely to go to the John Durkan as he’s now ineligible for the Drinmore at Fairyhouse in early December due to having won a Grade One last term.
“His end goals will all depend on how the season unfolds. His name has been thrown into the ring for the Gold Cup but it’s a big step up to go from your novice year to being up against the big boys. The John Durkan will likely be his first step and we’ll have a fair idea of what his level is after that. His jumping will need to sharpen up, so we’ll see how that progresses."