ED Upson has urged his teammates to "finish the job" after being ruled out for the rest of the season with an ankle injury.
The midfielder innocuously tweaked a ligament in his foot in training this week and will sit out the final four games of the campaign.
Scan results left the January signing feeling "absolutely gutted" but he will now be backing Millwall's fight for survival from the sidelines.
The Lions are just one point adrift of safety going into an Easter weekend double-header against Middlesbrough and Doncaster.
Upson, whose return to the side coincided with back-to-back wins at Nottingham Forest and Wigan, said: "It was just an accident in training. I rolled my ankle on the ball.
"I knew immediately that it wasn't good news because the pain was instant.
"The actual problem is a bit of ligament damage – thankfully it's not broken, but it's very swollen and painful.
"I'd been happy with my form – and even happier with the results – so I'm absolutely gutted to be honest, there are no other words to describe it.
"I will certainly be watching the remaining games – but it feels even worse when you are watching compared to when you're playing.
"I'll be like a nervous fan but I have a lot of faith in the boys. I truly believe that we can get out of it and that we will. I'll be cheering on from the sidelines like everyone else."
The 24-year-old was already ruled out of the Lions' trip to the Riverside on Saturday through suspension, having picked up his tenth yellow card of the season.
So that has made the timing of his injury even more frustrating.
"To get banned was disappointing and I was gutted after the Wigan game because I knew what the consequences were," Upson added.
"But this is a totally different feeling – it's even worse now. I was expecting to be back after the Middlesbrough game and ready to go again.
"I will try my best to get everyone going and give the lads as much encouragement and support as they need.
"We've got a few really important games coming up so it's a shame that I'm going to miss them, but I'll be there to support my teammates and hope that they can finish the job.
"I've got a lot of faith in them."
Manager Ian Holloway added: "It's really strange – Ed just stood on the ball. The last thing I wanted was for something like that to happen.
"Jimmy Abdou hasn't featured in the last few games so Ed's injury will give someone else a chance.
"For Ed it is a big blow because he's been doing well – I left him out, then brought him back in and the team started winning.
"The good news is that he'll be fit for next season – it's not career-threatening, it's just taken him out of the equation."