But the key defender has admitted that it took the best part of a week to recover from the bout of concussion he suffered against North Melbourne in round 10.
"I definitely wasn't right to play (against the Sydney Swans on Thursday night)," Lonergan told K-Rock radio on Monday morning. "I wanted to play, but the right call was made.
"I'd never been concussed before, so I wasn't sure about the symptoms. I thought I'd be OK. I woke up on the Saturday morning and thought, 'Oh yeah, I'll be fine.'
"I went for a drive and had to pull over. Mum was in the passenger seat and I said, 'Mum, you're going to have to drive here.' I was no good.
"I had blurry vision and all those things that you hear about. All Saturday and Sunday I was no good, and I was 10 to 15 per cent off all week.
"Most of the boys just thought it was normal for me, but it hung around and I couldn't shake it."
Lonergan's presence in Geelong's backline was sorely missed against the Swans, with the man who would have been his opponent, Lance Franklin, booting four goals as the Sydneysiders won by 110 points.
"I suppose you can think of it like an aberration," Lonergan said.
"But, to be honest … we didn't play our best footy against Richmond, Fremantle beat us up over there, and then Sydney.
"We've probably got a few things we need to iron out, and I'm sure Scotty (Chris Scott) has had a look at them over the weekend.
"It just goes to show that you've got to continually bring your A-game, because it's so even, the competition.
"If you don't, you'll end up with a performance like us on Thursday night".
The Cats are hoping another injured defender, Corey Enright, will recover from his ankle problem in time to take on the Blues.
The 32-year-old spent the weekend doing rehab on the ankle, which he first injured against the Brisbane Lions at the Gabba in round two.
"He would've been down the Torquay beach putting the leg in the water and doing all those things," Lonergan said.
"So I think it would've freshened the old boy up and he'll be ready to go."
Enright spoke about the injury while doing special comments during K-Rock's call of Saturday night's Dreamtime match.
"During the week it got a bit sore," he said. "With the six days (between games) we decided pretty early on that we wouldn't risk it.
"(I now have to) get through training and do everything that's required, but I'm feeling confident."
As for whether he'll have to manage the ankle problem for the rest of the season, Enright said: "Hopefully not. Hopefully we get on top of it now and put it to bed."
