Town were on course for a victory which would effectively have sealed their League One safety when they led the play-off chasers 2-1 with just 17 minutes to go at Highbury.
However, within 45 dramatic seconds Wednesday’s Lee Gregory bagged his second and third goals of the evening to condemn Town to another damaging defeat.
Town remain just outside the drop zone on goal difference but now it must go down to the final game of the season at Bolton on Saturday.
“I’m gutted for the lads again,” said Crainey after a thrilling ding-dong battle with the Owls.
“We responded really well to going behind early on and I thought we deserved to be 2-1 up at half-time.
“The lads played the game-plan to perfection and then at the start of the second half we contained Sheffield well.
“They got the equaliser and then we just switched off for the winning goal.
“A lack of concentration for that split second has proved very costly for us but that’s the reality of it
“At that point we knew it would be tough but it is really disappointing not to have taken anything from the game.
“The fighting spirit is still there. You can see that we’re not a team that’s defeated.
“Everyone at the game tonight could see that and now we’re going to need that fighting performance at Bolton on Saturday.
“We need to remain positive, dust ourselves down and go there and win the game. It’s still in our own hands, and that’s the big thing.”
Victory over Bolton would keep Town up and a point would be enough provided Gillingham did not beat second-placed Rotherham United.
Town can still lose on Saturday and stay up, though they would need the Gills to lose as well. In that case, MK Dons could still catch both clubs by beating Accrington Stanley, though they would need a goal difference swing of eight to overhaul Town.
Victories for Fleetwood and Gillingham could still send Morecambe down if they failed to beat Sunderland.