A wounded Lyon provided the iconic moment of this Ashes series on Saturday, batting with a badly injured calf to help Australia add 15 runs for the final wicket at Lord's.
Such was Lyon's state, the 35-year-old had to hobble down the stairs of the Lord's Pavilion one wicket early to ensure he was not timed out.
Still needing crutches to move properly, the 35-year-old then limped onto the field without them, used his bat as a walking stick and even hopped a single once in the middle.
The effort won him a standing ovation from Lord's and even a chant of his nickname Garry from sections of the crowd after he hit a four to help Australia set England a fourth-innings target of 371.
But it was met with questions in commentary, with Pietersen among those who asked what it would mean for the game if Lyon was hit in the head and became eligible for a concussion substitute.
"Imagine if he (Lyon) had been hit on the head and got concussion," Pietersen said.
"He'd have got a like-for-like replacement and a world class spinner (Murphy), based on how he performed in India. It gives food for thought."
Lyon hit out at the commentary after play on Sunday, given the Australian team's trauma following Phillip Hughes' death in 2014.
Lyon played 13 Tests with Hughes, and was on the field at the SCG the day he was fatally struck.
"I have heard comments that people thought I went out there to get hit in the head," Lyon said.
"I'm really against that because I've lost one of my mates due to being hit in the head. So I think that's a really poor excuse or conversation being had."
Ponting on Sunday used his first session on air to defend Pietersen and other colleagues.
"There was no way at all for any of us (were) saying that it'd be good to see Nathan Lyon get hit in the head and have a replacement," Ponting said.
"In fact, it was the other. It was almost the worst-case scenario for England; if they continued to bowl short and Nathan was hit.
"I just wanted to clarify that because there has been some negative chat around this morning, which has probably been a little bit unfair.
"By no means, no way at all would anyone ever hope to see somebody get hit in the head."
Lyon was due to meet with Australia's medical staff on Sunday to map out a recovery plan, but said he was shattered by the prospect his series was likely over.
"I have been absolutely shattered. I have been in tears, I have been upset, I have been hurting. That shows this team means everything to me," Lyon said.
"This is a little bump in the road. I can learn from it and get better. But right now, I am pretty shattered."
