The 35-year-old, who limped into the third Test but still took his tally of wickets to 16 in the two Ashes matches he has played, had a scan last night to assess the seriousness of an injury to his right elbow.
McGrath had a truncated role in training yesterday, but that initially appeared just to be the prerogative of the senior bowler. However, it then became clear that the man who has carried Australia's pace attack for a decade was in danger of missing the potentially decisive fourth npower Test, which starts here tomorrow.
The Australians had already one change in their bowling line-up with Shaun Tait selected ahead of Michael Kasprowicz to replace Jason Gillespie.
Australia's captain Ricky Ponting said Tait "might go for a few but has out-and-out wicket-taking ability".
Nowhere was the tension more apparent than in the Australian nets, where Tait, their aggressive young fast bowler, was involved in a altercation with the tourists' batsman, Justin Langer.
Tait, 22, struck Langer a painful blow with a pacy delivery. It was a shortish ball that caught the left-hander somewhere in his mid-section and dropped him to his knees in agony.
It looked serious enough to prompt the Australia coach, John Buchanan, to run 20 yards across the outfield to check on Langer. The batsman got to his feet, indicated he did not need treatment, then said something unprintable to Tait. Tait replied testily: "I'm not trying to pin you."
Langer, perhaps with his pride bruised too, had just been bowled by a very fast Tait delivery that swung back into him and hit off stump and the young quickie caught Langer again on a different part of his anatomy, prompting another curse.
With the series beautifully poised at one victory apiece (with one match drawn) Shane Warne was quick in pointing out that the Australians needed only to win one of the two remaining Tests to retain the Ashes. The pressure, he said, "is on England".
The England fast bowler Simon Jones wasted no time in rejecting that view. "We don't see how the pressure can be on us," he said. "We've been playing better cricket in the last two Tests."
Jones predicted that Matthew Hoggard, who has not had a big impact on the series so far, would play a significant part at Trent Bridge, a ground that traditionally favours swing bowlers. "It normally swings up here because of the atmosphere and the Trent [river] not far away," Jones said. "I think Hoggy will come into his own here.
"We bowl as a group. It's a great attack. We have got three 90-mph bowlers and there are not many sides who can boast that, and Hoggy swings it miles."
Warne admitted that a stiff back forced him to pull out of training yesterday, but insisted he would be fine tomorrow. As to who should replace Gillespie, Warne favours Tait's pace against the control of Kasprowicz. "Here you have a kid who is bursting at the seams and hitting blokes on the head left, right and centre," he said.
Tait, who is a 90mph plus bowler, later shook hands and had a conciliatory hug with Langer.Reuse content