Marin Cilic makes appearance on David Letterman's show, leaves everyone in splits

Marin Cilic poses with the winners trophy at the Top of the Rock Observation Deck at Rockefeller Center during the Champions New York City Trophy Tour.

Marin Cilic’s happiness after winning his first Grand Slam has been clear for everyone to see.

Smiling from ear to ear, the Croat toured New York city with the most prized possession of his career. And how could he miss being on the Letterman show when he was in town?

The veteran host was at his witty best as he asked tennis’s newest Grand Slam champion what was going through his mind during the most important match he has ever played. Without missing a beat, Cilic listed 10 hilarious things that were supposedly at the back of his mind as he looked to overcome Kei Nishikori in Monday’s final.

Watch the video for yourselves, and you will be convinced that the Croat can be a really funny guy when he wants to!