NEW YORK: They are both former champions and world number ones and at the US Open starting on Monday Maria Sharapova and Kim Clijsters will both attempt to crown stunning comebacks to the WTA circuit.

In the case of Sharapova it was a chronic shoulder injury that forced her onto the sidelines for nine months and left her at times fearing that her remarkable career could be over at the tender age of 22.

Clijsters, in contrast, walked away voluntarily from the sport at the age of 23 in May, 2007 citing injuries and her pending marriage. Two months later she gave birth to daughter Jade Ellis. Sharapova finally returned to action in May where she reached the quarter-finals of the Warsaw claycourt tournament.

Since then the Russian has compiled a 22-7 win-loss record reaching the quarter-finals at the French Open before bowing out in the second round at Wimbledon.

But significantly she has produced her best tennis in over a year at two build-up tournanents to Flushing Meadows reaching the semi-finals in Los Angeles and the final in Toronto where she lost to compatriot Elene Dementieva.

Sharapova has made it clear she will not be competing in New York, where she won the second of her three Grand Slam titles in 2006, just to make up the numbers and show off her new designer diamond earrings.

"My mindset going into every single tournament is obviously to be the champion. If you're not ready to do that and you're not ready to compete for six or seven matches, then I don't think you should be in the draw," she said.

"So you always have that positive attitude, and with every tournament that I played in the summer, I felt like I was starting to play better and get a good feel for the hardcourts. "After the grass season I put a lot of work in outside the court. I've definitely improved over the weeks and with every match I felt like I stepped it up when I had to." The Clijsters comeback is more recent as the Belgian player competed for the first time in over two years at Cincinnati earlier this month stunning top-tenner Marion Bartoli in the first round en route to the quarter-finals where she came close to taking a set of world number one Dinara Safina, She then reached the third round in Toronto before losing in three tough sets to world number five Jelena Jankovic.

Clijsters, who won her only Grand Slam title here in 2005, believes that she still has something to offer at the top level.

"I think a lot of the girls these days that are up there, they play a very similar game," she said.

"They play tennis like this is a perfect game, playing that aggressive tennis, stepping in and just really hitting the ball over the net and not giving your opponent a lot of chances.

"But on the other hand, if that doesn't go the way that they want it to go, I feel like the plan B is not always there.

"And that's something that a lot of girls -- Venus, Serena, even Justine, even myself -- even if we're not playing our best game, we can still work on -- we still have a plan B." The chances are that neither Sharapova nor Clijsters will have the consistency to keep on winning throughout a two-week long tournament, but one thing for sure is that none of the favourites will want to cross their paths in the early rounds.