Former world number one Maria Sharapova is growing in confidence and feels she can challenge for the US Open as the five-time grand slam champion draws inspiration from the evergreen Roger Federer.

Sharapova battled through to the third round of the US Open after overcoming Timea Babos 6-7 (4-7) 6-4 6-1 at Flushing Meadows on Wednesday.

The 30-year-old Russian star is featuring in her first slam since the 2016 Australian Open, having tested positive for a banned substance at Melbourne Park last year.

Sharapova returned from a 15-month suspension for violating anti-doping rules in April, but was denied a wildcard for the French Open and then pulled out of Wimbledon qualifying through injury.

Granted a wildcard for the year's final slam, Sharapova – who missed the Western & Southern Open and Rogers Cup due to injury – is back and winning as she looks to add to her 2006 US Open crown.

"I certainly have expectations just because I know I've been in these stages before and I've been able to execute," Sharapova told reporters.

"There's a certain level of I know I can do this, I've done it before. I want to have that feeling again.

"But there's also the realistic understanding of, Okay, you haven't been in this situation for a while. It's going to take a little time.

"Of course, managing expectations is part of it, learning as you play the matches, which is something I haven't done for a long time."

Sharapova, who faces Sophia Kenin in the next round, added:  "I still think I need a little bit more time, a little bit more matches. I'm definitely a player that likes and prefers to play with instinct.

"I like the moments where you have to figure it out on yourself. Obviously you go into a match with a little bit of a plan on how you're going to play and execute. But there are times in a match where you just have to, as you say, play with instinct.

"So that's definitely a preference of mine. It will take a little bit of time. But today was maybe not a match where I showcased that."

Sharapova is also taking inspiration from 19-time grand slam winner and 36-year-old Roger Federer, who missed most of last year through injury.

Since returning to the court, Swiss icon Federer has won the Australian Open and Wimbledon this year.

"What he's done is incredible. I think not just myself, but a lot of people can take a lot of inspiration and motivation from what he's done. That's very special to see, just the passion with which he still plays and the level and the quality and the consistency.

"Those are all things at his age, after everything he's accomplished, personally that's what I always see in champions, in Roger and Rafael [Nadal], Serena and Venus [Williams], that they're still able to produce, not just produce that type of tennis but want to be there and want to compete and want to win.

"They've done it, they've been around the world, done it over and over again. To have that passion I think is what makes it so special."