South Africa great Jacques Kallis knows England will be unable to directly replace Ben Stokes if the star all-rounder is not able to face Australia in the Ashes.
Stokes has not travelled with the squad and will not be considered for selection by the England and Wales Cricket Board (ECB) until the conclusion of a police investigation following the player's arrest on suspicion of causing actual bodily harm in Bristol in September.
One of the best all-rounders in the history of the sport, ex-Proteas stalwart Kallis knows exactly how important such versatility can be to a team's hopes in the longest format.
"It'll be a massive loss, he's two players in one," the 42-year-old told Omnisport.
"All-rounders are so valuable. And he's a world-class all-rounder. I've really been impressed how he's come on as a player. England need him. Hopefully they can sort it out but I think they've gone about it the right way.
"It's difficult to replace an all-rounder... England have to make sure their fast bowlers do the work for them. It's going to be a tough, interesting series. We're all looking forward to it. It'll fun to watch I think."
Kallis faced Australia on their own turf in Tests on 14 occasions, winning just three times, meaning he is well acquainted with the scale of the challenge facing England.
"Tough place to tour, Australia. It really is a tough place," he said.
"England are going to have to play some good cricket to beat them. They really are going to have to. It's a different ball, the Kookaburra is different to the Duke. That, for a start, is a big difference.
"Australia at home - tough to beat. I'm 50.1 per cent and 49.9 per cent favouring Australia but it can go any way. It's going to be who plays those important days better. But I think [it will be] pretty evenly matched."
Asked if he expects another 5-0 whitewash, which has been England's fate in two of their last three Ashes series in Australia, he said: "I can't see that happening. I think it's going to be close. I think both sides will play positive cricket, most of the Test matches we'll get a result.
"I'm going to throw my neck out there and say maybe Australia, they'll just pip them. But I'm not saying that's going to be 100 per cent correct."
The first Test between Australia and England starts at the Gabba in Brisbane on November 23.