Tim Henman believes competing in multiple rounds of five-set matches with limited recovery time "may be a step too far" for former world number one Andy Murray.
Murray is set to play at the US Open from August 30, for what will be his first grand slam tournament since pulling out of the Olympic singles event in Tokyo last month with a thigh injury.
The 34-year-old was encouraged by his movement during the recent Cincinnati Masters, in which he was knocked out by world number 13 Hubert Hurkacz in the second round, and Henman believes his improvement is evident.
"I think it (his recovery) has been great. You want to look at his trajectory of his path of improvement, and the way he played at Cincinnati last week," Henman told the PA news agency.
"I thought it was a very good win against (Richard) Gasquet who's still a top-50 player, against Hurkacz, who's one of the form players of the year, it was a tight match and he had set points in the first set.
"If the Andy Murray of today played the Andy Murray of the first round of Queen's I think he beats him very easily and so things seem to be moving in the right direction. The biggest challenge is whether he can stay injury-free, he's been so stop-start for the last four years."
He added: "We can't really judge where Andy's level is at unless he plays three, six, nine months of tournament tennis.
"If he's able to do that I think he can improve his level significantly from where he's at now.
"Can he compete best-of-five-set matches in slams and come back with the recovery? I think that may be a step too far but certainly on the tour and in the ATP Masters I definitely think he can be competitive."
After going out in Cincinnati, Murray decided to get in more match practice at the Winston-Salem Open, before heading to New York and the US Open.
It has been a difficult last four years for the Scot, including two hip surgeries, one in 2018 and one the following year with a groin injury and a thigh problem also among the recent setbacks.
"I love to hear his motivation," said Henman. "When we did an interview with him for Prime Video in Cincinnati, he really didn't feel like he was at the end of his career, he wanted to keep playing and keep challenging himself and I think that's absolutely right.
"(Being) a professional athlete is the best job in the world and it doesn't last forever so as long as he has the hunger and desire and motivation to keep putting the work in, and he feels like he's being rewarded enough on the match court, then he should play as long as he wants to."
Regarding the US Open itself, Henman admitted Novak Djokovic remains a "clear favourite" to lift the title, and by doing so the Serbian would become the first man to lift all four grand slam titles in a single calendar year since 1969.
"There's no doubt that Djokovic is the clear favourite, his form in the majors has been incredible – it speaks for itself," said former British number one Henman.
"To play so well on hard courts, clay courts, grass courts, I think it really emphasises what a complete player he is.
"So when I reflect on the chances of him completing all four I think it's Djokovic against the field but I think there's also the plus one in the occasion is history.
"There's no doubt as a student of the game that he's very aware of what's on the line, so it'll be interesting to see how he deals with the opposition on the other side of the net but also internally, because it's a massive opportunity. I think it's going to make it a fascinating fortnight."
:: Henman will be working for Prime Video during The US Open which is available to watch from Monday 30th August.
