Wales flanker Lydiate's World Cup future hung by a thread only three weeks ago after he suffered ankle ligament damage just 10 minutes into the Pool D clash against Samoa.
There was a possibility he would be forced out of the tournament, but Lydiate's ferocious commitment towards regaining full fitness paid off as he was reunited in winning fashion with back-row colleagues Sam Warburton and Toby Faletau.
"In the dressing room afterwards I think Dan was that tired he couldn't take his shirt off," Wales boss Warren Gatland said.
"He did what we asked - he emptied the tank. He hadn't played for a few weeks, but he has worked so hard off the field."
Lydiate's recovery regime including getting up at two-hourly intervals during the night to ice his ankle, all aimed at being able to rejoin Wales' great World Cup adventure.
"I was gutted to get injured, but it's part and parcel of the game," Lydiate said.
"There was a chance I would be going home, but I tried to do everything in my power for that not to happen. I was happy to get on the field again.
"It was no more than anyone else would do, really. It was about being diligent with your icing times and being on time with your physio appointments, but every rugby player would be the same, I guess.
"I didn't leave anything in the tank out there, but it is all about getting the result. Every time you put the jersey on that's what you want.
"I just wanted to go flat out as long as I could, chuck my body in there, and I got through it, just about.
"It is hard to put into words what this all means. There were a few tears and that afterwards. We are just so happy.
"But come tomorrow, we have got to be getting ready for next weekend. It won't go to our heads. We are out here to do a job."
Lydiate's performance was showcased in defence, where Wales produced a memorable display during the first half, especially, by nullifying Ireland's attack, both wide out and at close quarters.
"We had been through the mill pre-season, and we backed our conditioning," he added.
"In the first 40 minutes, we defended for our lives, Our conditioning really got us through it.
"The Irish back row are big powerful men, and it was a case of trying to stop them before they get going. The likes of Sean O'Brien and Stephen Ferris, once they get going they take a lot of stopping.
"At half-time it was a case of just keeping going. We had to keep our composure and keep plugging away. The boys really put their hands up in defence."
Wales can now look forward to meeting France in Auckland next Saturday - their first World Cup semi-final appearance for 24 years.
"We work hard for each other - we are one big tight unit," said Lydiate.
"They called our group the 'pool of death,' and I think our conditioning really helped us get through. We haven't picked up too many injuries.
"We are in the semi-finals now, and we have just got to push on."
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