Graeme Swann's arm injury is a timely reminder that England's bid to retain the Ashes can be badly dented by just one delivery, says Nick Knight.
Spinner Swann suffered a bruised arm at the crease when he was struck by Essex bowler Tymal Mills on day two of the warm-up match at Chelmsford on Monday.
The 34-year-old carried on with his innings and made 94 but subsequently went for an X-ray which confirmed that there was no fracture.
However Sky Sports pundit Knight reflected: "It will have been an anxious couple of hours or so.
"The good news was that he batted on but when he went for an X-ray if there had been any chip or fracture in there that would have probably have taken him out of the Ashes.
"It was a big moment and I'm glad he's ok. It's hard to imagine a greater loss to the England team right now than Graeme Swann.
"You could mention Kevin Pietersen and Jimmy Anderson but with those left-handers in Australia's team you want Swann in your side."
Former England all-rounder Dominic Cork agreed that the loss of Swann, who has 222 Test wickets to his name, would have been a damaging blow with the Ashes only a week away.
"It would have really dented England to have lost Swann now because he's such a vital cog in the team and he's also a character in the team, who knows how to win the Ashes," Cork said. "Thankfully - and hopefully - he'll be fit and raring to go."
Meanwhile, Australia have confirmed that Shane Watson and Chris Rogers will open the batting in the opening Ashes Test at Trent Bridge.
Rogers - who counts Derbyshire, Leicestershire, Middlesex and Northants amongst his former teams - made his only Test appearance over five years ago but Bob Willis believes new Australia coach Darren Lehmann has picked wisely.
"That's an important decision for Australia to have made and I think it's good to make it early and not keep the players wondering what is going on," said Willis.
"Watson and Rogers give them some experience at the top of the order although, admittedly, Rogers is not that experienced in Test match cricket.
"But he's spent season after season in the county game getting used to conditions over here. With Michael Clarke in the middle-order it doesn't bode well for the likes of David Warner and Philip Hughes getting a spot in the top five in the order but it would look as if one of them would have to play.
"This Australia squad has now swelled out to 18 individuals, so seven players aren't going to be playing at Trent Bridge.
"They may be getting towards finalising their batting line-up but they are still making up their minds about the bowling line-up - the bowlers who didn't have a go at Taunton are having a go at New Road."