Serena Williams has spoken of her close friendship with tennis rival Caroline Wozniacki . Appearing on the front cover of US Vogue , the American world No 1 admits that times can get tough at the top and that she is glad to have Wozniacki and sister Venus around for support . 'It ’ s hard and lonely at the top , ' Serena confessed to Vogue . 'That ’ s why it ’ s so fun to have Caroline and my sister , too . You ’ re a target when you ’ re number one . Everyone wants to beat you . Everyone talks behind your back , and you get a lot more criticism . God forbid I lose . ' Scroll down for video . American world No 1 Serena Williams appears on the front cover of Vogue and showed off her fit physique . Serena shared an Instagram image touting her Vogue issue in which she admitted : 'It ’ s lonely at the top ' Last May , it was Caroline who needed Serena 's support . When Serena got word that Caroline had been dumped by fiance Rory McIlroy , she immediately picked up the phone . ' I was devastated . I had planned the bachelorette party , ' Williams said . Serena and Caroline both sat down to chat about the event six months after the fact . 'My phone was going crazy , but I didn ’ t want to talk to anyone , ' said Caroline . ' I kept calling , ' Serena said . 'First she texted , `` If you don ’ t pick up , I am going to fly to Monaco . '' And then , `` If you don ’ t answer the door , I am going to knock it down . '' 'So I thought , OK , I better answer the phone . And I am so glad I did . She wasn ’ t pitying me , like a lot of people were . I mean , it ’ s not like anyone died . ' Williams spoke about her close friendship with Caroline Wozniacki , who is a rival on the tennis court . Wozniacki added : ' I was in shock , but she was really helpful because she had been through it before . She didn ’ t sugarcoat it , and she didn ’ t look down on me . 'She was really there for me when I needed her the most , and that ’ s why I think our friendship is so strong now . ' ' I was impressed with how strong she was , ' Serena said , before continuing : 'And you know , there will be other engagement parties ... many . ' Williams and Wozniacki celebrate after the Dane finished last year 's New York Marathon while the pair also attended the Vogue Fashion Fun Awards in New York last year . Serena indicated that Caroline wo n't have problems finding another guy , as they literally swarm her when the girls go out at night . ' I am really shy . I don ’ t talk to guys , ' Serena conceded . And although she had once wished for a family and children of her own some day , she 's not in any particular hurry . ' I guess , ' she said . ' I ’ m not even looking for it . ' On the court , it 's a different story . Serena went on to say : 'On the court , I am fierce ! I am mean and I am tough . I am completely opposite off the court . My confidence just isn ’ t the same . I wish I was more like I am on the court . Nobody would know that I am constantly crying or complaining . ' Williams said : 'On the court , I am fierce ! I am mean and I am tough . I am completely opposite off the court '
World No 1 Serena Williams appears in the April issue of US Vogue . The American admits ' am not a great tennis player Williams is pleased to have tennis rival Caroline Wozniacki as a friend .