Moeen was on 11 when he pulled up lame while running between the wickets during the second session, and although he carried on to make a rapid 34 runs after receiving medical attention in the middle, he didn’t take to the field when it was England’s turn to bowl.
The injury blow has rattled England in its pursuit of a series-levelling victory at The Oval.
After being bowled out for 283 runs, the English were without Mooen as the Australians climbed to 1-61 at stumps on the first day.
And even if Moeen recovers overnight, he won’t be allowed to bowl for most of day two’s opening session given he was off the field for 25 overs.
“Moeen Ali has a right groin injury,” the England and Wales Cricket Board posted on Twitter during the third session.
“He will continue to be assessed and will not field for the rest of today.”
Moeen had made 11 runs from 38 balls when he sustained the injury, before hammering 23 runs — including two fours and a couple of sixes — off his next eight deliveries.
He lost his wicket when he tried to swat off-spinner Todd Murphy across the line, only to miss the ball and have his stumps rattled.
“As soon as the physio left the pitch he was like: ‘Should I just tee off now?'” said Harry Brook, who was batting with Moeen when he suffered the injury.
“”I said: ‘You should have been doing that from the start’.
“He’s one of the best power-hitters in the world so there’s not many better men to have out there if you want him to go and smack it. The way he went about it after his injury was perfect. We could have easily got (some singles), because they started to put everybody back as soon as he played a few big shots.
“But he was in a lot of pain so there weren’t going to be many twos.”
Since being elevated from England’s lower order to first drop in the fourth innings of the third Test, Moeen has tallied five, 54 and 34.
The 36-year-old has struggled to trouble the Australians with the ball since being pulled out of retirement for this series following Jack Leach’s injury blow.
Having not played red-ball cricket since September 2021, his spinning finger deteriorated badly in the first Test.
He was docked 25 per cent of his first-Test match fee after being spotted using a drying agent on his spinning finger.
He completed 47 overs in the first Test but was visibly hindered by his finger falling apart.
Highlights: Fifth Ashes Test, day one
A silver lining for the English is part-time off-spinner Joe Root has caused the Australians headaches in this series.
England captain Ben Stokes was frustrated when the umpires ruled on day four of the Old Trafford Test that he could no longer bowl his quicks, but Root was brought on and made the going difficult for Marnus Labuschagne.
He almost had Labuschagne caught at first slip on 93, before having Australia’s first drop caught behind on 111.
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