Karolina Pliskova believes it will be "super difficult" for Serena Williams to challenge for another Grand Slam title at Wimbledon after a year away from tennis.
Williams, 40, made the shock announcement last week that she would be returning at the third major of the season.
Williams hasn’t played since suffering a leg injury in the first round of Wimbledon in 2021, but is competing in the doubles at this week’s Eastbourne International with Ons Jabeur before trying to win an eighth Wimbledon singles title.
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Pliskova, who lost to Ashleigh Barty in last year’s Wimbledon final, thinks Williams could find it tough going on her return.
"I don't know how long it has been since she has played. Has it been a year? It is a long time and she is not the youngest any more so I suppose the body also takes some time to get back into shape.
"Playing matches at tournaments is still very much different to just practising and from what I understand, she is not playing (singles) here [in Eastbourne], she is just playing doubles.
"I think it will be difficult, super difficult for her no matter which kind of player she is because this is a thing where you still need some time.
"But of course, she is an amazing player, she achieved so much and still a number of players will be super scared to play her. This is her advantage but let's see the level. I cannot really say."
Pliskova holds a 2-2 win-loss record against Williams and won their most recent meeting in the quarter-finals of the 2019 Australian Open.
Williams is still bidding to win a 24th Grand Slam title to equal Margaret Court’s all-time record.
Despite doubts over Williams’ fitness, world No. 4 Paula Badosa says she does not want to face the American at Wimbledon.
"I think it surprised everyone but it's very good to have her back. It really amazes me how she has all this hunger for the game," said Badosa.
"It is a great inspiration. It is nice to have her back and I hope she can be back for much more time because I think she does very good for tennis.
"But the other side, of course I don't want to play against her! I hope the draw goes for another player because no one wants to play against Serena and less on grass. Let's pray for that!"

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Williams and Jabeur will play unseeded duo Marie Bouzkova and Sara Sorribes Tormo in the first round on Tuesday, and if they advance will take on either No. 4 seeds Lucie Hradecka and Sania Mirza, or Shuko Aoyama and Chan Hao-Ching.
Jabeur says she is "excited and nervous" about playing alongside Williams.
"I wanted to tell everyone, but obviously I couldn't," the world No. 3 told the WTA Tour.
"I told my family, but even my close friends, I didn't tell anyone.
"Excited, really lucky that she picked me. I'm pretty glad that I can share the court with her. I always watched Serena playing and always supported her.
"She's such a legend and such an example for our sport. I'm really nervous to play. I hope the match will be great and we'll have great matches.
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Watch daily highlights from Wimbledon at 10pm on Eurosport 2 and discovery+ from June 27, as well as the two singles finals live on July 9 and 10.
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