Australian off-spinner Nathan Lyon might have suffered a "significant" calf injury that is all but certain to have ended his Ashes campaign, but it didn't stop him from batting during Day 4.

With Australia attempting to build their lead to an insurmountable margin for the English, Lyon hobbled to the crease, adding four runs of his own in a 15-run last-wicket stand with Mitchell Starc, who finished 15 not out.

In what could have been the 35-year-old's final act in an Ashes series, and almost certainly his final one on an English ground, Lyon helped Australia build the lead to 370, with England needing 371 to win.

The hosts sit at 4 for 114 at the end of play on Day 4.

But it was a comment in commentary from Kevin Peitersen that drew the ire of Lyon, with the former batsman suggesting Lyon may have batted in hopes of being hit to trigger a concussion replacement.

โ€œImagine if he [Lyon] had been hit on the head and got concussion, he'd have got a like-for-like replacement and a world-class spinner Todd Murphy, based on how he performed in India, it gives food for thought,โ€ Pietersen said on Sky Sports during the coverage of Day 4.

Lyon, speaking post-game, slammed that as an idea, reminding the media he had lost good mate Phil Hughes, who passed away in 2014 after complications from being hit in the head during a Sheffield Shield match at the Sydney Cricket Ground for South Australia against New South Wales.

โ€œI have heard comments that people thought I went out there to get hit in the head, and I'm really against that because I've lost one of my mates due to being hit in the head,โ€ Lyon said.

โ€œSo I think that's a really poor excuse or conversation being had.โ€

There have been suggestions Lyon - who has taken more than 400 Test wickets - could retire, however, he refuted that suggestion, wanting to make his return.

โ€œIt's been a lot down more than up. I have been absolutely shattered. I have been in tears, I have been upset, I have been hurting,โ€ he said. โ€œThat shows this team means everything to me. And I will start this rehab journey now to get back and play my role and keep loving what I am able to do.

โ€œI've got a decent tear in my right calf. It is pretty obvious. I am sitting down with our medical team tomorrow and we will have a chat about that. Pretty shattering, pretty gutted. Pretty speechless if I am being honest. But I have a lot of confidence in that changeroom and just thrilled to be part of this team.

โ€œThis is just a little speed bump in the road. This isn't career-defining. I am hungrier than ever to get back out there, especially when you see your teammates out there busting your guts this afternoon. It's disappointing from my end and the guys will keep going on and we will go from there.โ€

Australia doesn't have another red ball commitment until mid-December when the summer of cricket starts against Pakistan, with three Tests against the sub-continent nation to be followed by two against the West Indies. Australia is then slated to travel to New Zealand in February and March for two Tests.

Todd Murphy will likely come into the Australian side for the final three Tests of this year's Ashes series, with Australia looking to go up 2-0 on Day 5 at Lord's.