Marnus Labuschagne just wanted to "get up and try to act cool" after being struck by a short ball from Jofra Archer on the final day of the second Test against England.

After replacing the sidelined Steve Smith in Australia's side, in the process becoming the first concussion substitute in Test history, Labuschagne endured a tough Ashes baptism as Australia attempted to bat out for a draw.

Coming in with the score at 19-2, the right-hander was unable to avoid his second delivery at the crease, a rapid bouncer from Archer crashing flush into the grille of the helmet.

The batsman quickly bounced back to his feet following the blow and was cleared by the team's medical staff to continue his innings. He went on to make 59, a pivotal contribution as the tourists survived to retain their slender 1-0 lead in the series.

Asked what he was thinking immediately after the impact, Labuschagne said: "You get up and try to act cool.

"It was then about trying to refocus and make sure you're watching the ball again - I was watching that one pretty closely!

"You just want to stay calm and answer the questions [from the medical staff] properly. I was like, 'I know where I am, I'm good. Get off the field!'. There's a process now, but there was no way I was going to get off that field.

"You want to stay in the contest. Getting to play at Lord's is a pretty great experience, so you just want to make sure you're ready, listen to their instructions and follow them - that's the key.

"If you have to come off, it's obviously because you're not alright. In my case, I was feeling fine. I just jumped the gun a bit on the questions. I knew how many I was on - 'I'm on zero and that was a fast bouncer'."

It was a similar delivery from Archer that hit Smith on day four. Australia's former captain retired hurt and, while able to return to the crease to continue his innings later in the session, he was ruled out of playing any further part in proceedings on the final morning due to delayed concussion.

Archer claimed five wickets in what was an impressive Test debut, as noted by Labuschagne.

"He bowled really well, at times his length was really good, and he obviously tested us with the short stuff on this up-and-down wicket," the 25-year-old said.

Despite not being able to bat in his side's second innings, Smith has climbed up to second in the updated International Cricket Council's Test rankings for batsmen and now trails leader Virat Kohli by just nine points.