Mitchell Johnson was disappointed by those in the Lord's crowd who opted to jeer returning Australia batsman Steve Smith during a dramatic fourth day of the second Ashes Test.

Smith was forced off hurt on Saturday after a rapid short ball from Jofra Archer struck the right-hander just below the helmet.

The 30-year-old left the middle but, after passing the required concussion tests, returned to bat later in the innings, eventually dismissed for 92 as Australia made 250 all out.

However, Smith did not field in England's second innings, with Australia confirming their former captain would play no further part in the Test - Marnus Labuschagne taking over as a concussion replacement.

While the majority of the Lord's crowd gave Smith - who has been the recipient of rough treatment from some England supporters throughout the series following his involvement in the 2018 ball-tampering scandal - a standing ovation when he made his way back out onto the field, some boos were audible, and Johnson was angered by such behaviour.

"One of the biggest disappointments for me was the crowd," said Johnson told ESPN Cricinfo.

"Not the whole crowd, obviously, but a couple of boos could be heard through the stump mic, and that really disappointed me when he came back out to bat.

"I don't care what people say, they can say 'yes, he's a cheat and that's why we're booing him', but that's a load of rubbish to me.

"Yes, he's done what he's done, and you can boo him at the start of play when he comes onto the field if that's how you feel. But for me, he's taken a heavy knock - two heavy knocks - but he's said, 'I can still bat here'.

"He's braved up, he's come through the concussion tests, and not many people would be able to do that."

Johnson also defended England duo Jos Buttler and Jofra Archer, who received some criticism on social media when a video circulated which appeared to show the players laughing while Smith received treatment.

"I was on the radio when it happened, and I found it quite difficult to speak at the time because of the way Smith hit the ground and lay there," Johnson said. "You could see he was moving around, but it obviously hurt him.

"In that situation they did everything they could as players. They made sure he was okay as best they could. They are not professionals in the medical world, so they have to leave that up to the professionals to make those decisions and sort that out.

"There was a bit of nervousness in the laughter. Archer was a bit shaken by it, he's a cool character, really calm, but you could tell in his eyes there was a little bit of concern there as well."