Eighteen years ago, key Australia seamer McGrath trod on a ball in the warm-up at Edgbaston and missed an Ashes Test England went on to win by two runs. It felt like a series-shifting moment.

Fast forward to the present day and the calf injury Baggy Greens off-spinner Nathan Lyon sustained on day two of the Lord's Test could have a similar impact.

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Australia are waiting anxiously for further news after Lyon pulled up in the field in Thursday's evening session and had to be helped off by a member of support staff.

The look on Lyon's face as he departed suggested his problem was serious and if that proves the case it will significantly boost England's hopes of regaining the Ashes for the first time since 2015.

Speaking at stumps, Lyon's team-mate Steve Smith said the outlook "doesn't look good".

Smith told reporters: "It doesn't look ideal for the rest of the game. I'm not sure how he actually is, but if he is no good, it is obviously a big loss for us. Fingers crossed he is okay but it didn't look good obviously."

It would be a cruel blow for Lyon, who in this game became the first specialist bowler to play 100 consecutive Test matches.

Team-mates and pundits were lauding his consistency, fitness and skill, now they must wait to see if he plays any further part at Lord's and perhaps even the series.

Lyon picked up eight wickets during Australia's win in the first Test at Edgbaston and his dismissal of Zak Crawley on Thursday afternoon took him up to 496 wickets in Test cricket. Only seven players, including McGrath, have more.

He offers captain Pat Cummins control and penetration.

Speaking to Sky Sports, Sir Andrew Strauss said of Lyon's injury: "If you look at the teams side by side, he is the major difference. He gives Australia balance and is a threat no matter what the conditions. It would be a massive loss.

"Let's see, but you would have thought he would play little part in the rest of this Test match at least."

Kevin Pietersen added: "You could see from the way he walked around the boundary that he had all the weight on the right side of his foot. I think he has popped a calf and if you pop a calf you are not coming back from that for a while."

If Lyon's injury rules him out long term, Australia could call upon Todd Murphy for next week's third Test at Headingley and beyond.

Off-spinner Murphy is yet to feature in an Ashes Test but played four times in India earlier this year, taking 14 wickets at an average 25.21 with a best of 7-124 on debut in Nagpur.

Smith said: "Todd has been bowling beautifully in nets and bowled really well in India when he got his opportunity. I would be confident if he came in that he would do a terrific job for us."

For the rest of the Lord's Test, Australia will have to rely on the part-time spin of Travis Head, Steve Smith and Marnus Labuschagne if Lyon is crocked.

England batter Ben Duckett said: "It is a huge shame. I really hope it's not too bad for him. You never want to see anyone go down with an injury.

"He was going to play a massive part in that fourth innings because he is such a good bowler. If he can't bowl it is going to be a massive miss for them."

England ended day two on 278-4 and just 138 runs behind Australia, with the tourists having been bowled out for 416 in the morning session after losing their final five wickets for 73 runs.

Watch day three of the second Ashes Test, from Lord's, live on Sky Sports Cricket on Friday. Build-up starts at 10.15am ahead of the first ball at 11am. You can also stream with NOW.