![Kiefer criticizes Zverev and Thiem: "Questioning whether they have anything other than tennis balls in their heads · tennisnet.com Kiefer criticizes Zverev and Thiem: "Questioning whether they have anything other than tennis balls in their heads · tennisnet.com](https://www.tennisnet.com/fileadmin/_processed_/d/1/csm_nicolas-kiefer_0ba1ca58f3.jpg)
Kiefer criticizes Zverev and Thiem: "Questioning whether they have anything other than tennis balls in their heads · tennisnet.com
![Tennis player Nicolas Kiefer of Germany celebrates after winning his match against Juergen Melzer of Austria at the ATP Masters tournament in Hamburg, northern Germany, on Tuesday, May 16, 2006. Kiefer won Tennis player Nicolas Kiefer of Germany celebrates after winning his match against Juergen Melzer of Austria at the ATP Masters tournament in Hamburg, northern Germany, on Tuesday, May 16, 2006. Kiefer won](https://c8.alamy.com/comp/2PD3163/tennis-player-nicolas-kiefer-of-germany-celebrates-after-winning-his-match-against-juergen-melzer-of-austria-at-the-atp-masters-tournament-in-hamburg-northern-germany-on-tuesday-may-16-2006-kiefer-won-6-2-3-6-6-2-ap-photokai-uwe-knoth-2PD3163.jpg)
Tennis player Nicolas Kiefer of Germany celebrates after winning his match against Juergen Melzer of Austria at the ATP Masters tournament in Hamburg, northern Germany, on Tuesday, May 16, 2006. Kiefer won
![Nicolas Kiefer of Germany in action during his match against Rafael Nadal from Spain on day 5 of the US Open at the USTA Billie Stock Photo - Alamy Nicolas Kiefer of Germany in action during his match against Rafael Nadal from Spain on day 5 of the US Open at the USTA Billie Stock Photo - Alamy](https://c8.alamy.com/comp/C1Y5X3/nicolas-kiefer-of-germany-in-action-during-his-match-against-rafael-C1Y5X3.jpg)
Nicolas Kiefer of Germany in action during his match against Rafael Nadal from Spain on day 5 of the US Open at the USTA Billie Stock Photo - Alamy
![Nicolas Kiefer, Germany, playing a backhand, tennis, the ITF Grand Slam tournament, French Open 2009, Stock Photo, Picture And Rights Managed Image. Pic. IBR-1186941 | agefotostock Nicolas Kiefer, Germany, playing a backhand, tennis, the ITF Grand Slam tournament, French Open 2009, Stock Photo, Picture And Rights Managed Image. Pic. IBR-1186941 | agefotostock](https://previews.agefotostock.com/previewimage/medibigoff/0fd978c8fe70bbffe541609013da583a/ibr-1186941.jpg)
Nicolas Kiefer, Germany, playing a backhand, tennis, the ITF Grand Slam tournament, French Open 2009, Stock Photo, Picture And Rights Managed Image. Pic. IBR-1186941 | agefotostock
![German tennis pro Nicolas Kiefer looks frustrated during his match against Belarusian Mirnyi at the ATP German Masters in Hamburg, Germany, Wednesday, 17 May 2006. Kiefer lost the match in two sets German tennis pro Nicolas Kiefer looks frustrated during his match against Belarusian Mirnyi at the ATP German Masters in Hamburg, Germany, Wednesday, 17 May 2006. Kiefer lost the match in two sets](https://c8.alamy.com/comp/D3NHRG/german-tennis-pro-nicolas-kiefer-looks-frustrated-during-his-match-D3NHRG.jpg)
German tennis pro Nicolas Kiefer looks frustrated during his match against Belarusian Mirnyi at the ATP German Masters in Hamburg, Germany, Wednesday, 17 May 2006. Kiefer lost the match in two sets
![Nicolas Kiefer at the Los Angeles Tennis Open Editorial Stock Image - Image of wide, professional: 11418909 Nicolas Kiefer at the Los Angeles Tennis Open Editorial Stock Image - Image of wide, professional: 11418909](https://thumbs.dreamstime.com/z/nicolas-kiefer-los-angeles-tennis-open-11418909.jpg)