But since the turn of the year the 27-year-old has slowly but surely worked his way back into contention for both club and country, featuring in England's final two games of the RBS 6 Nations.
Such has been Croft's remarkable return to form and fitness that the blindside flanker was included in Warren Gatland's British and Irish Lions squad ahead of Quins and England skipper Chris Robshaw.
And Croft underlined his Lions credentials in destroying Harlequins in the play-off semi-finals at Welford Road as he ran in the third of his side's four tries in a 33-16 win, a 50 metre solo effort that left any would be tacklers grasping at thin air and O'Shea running out of superlatives.
"Tom Croft is a very special athlete," O'Shea said. "But it is also the physicality he brings to the game - he is an incredible competitor."
And Croft's own director of rugby Richard Cockerill agreed with his rival's assessment of the flanker.
"We know how good Crofty can be. We have been very patient with him, and he's been very patient with us. Our loyalty to those guys who get injured is always the same," he said.
"But the commitment from those six Lions today, you wouldn't think they were saving themselves, would you?"