American tennis player Steve Johnson has won in four sets against Croatian Borna Coric in his second round match at Roland Garros.

The 27-year-old said the recent death of his father has left him an “emotional mess” after the Californian sank to his knees and cried on court following his win at the French Open.

Johnson, whose father was a tennis coach, credits him with introducing him to the sport and spoke about him after the match.

"I just miss my dad," Johnson told the Tennis Channel.

"I wish he was following along - I know he is from upstairs - but it's just so emotional, it's hard to describe.

"I just knew he was looking down on me on that last point and gave me the strength to finish it off."

Johnson’s father Steve Johnson Sr passed away earlier this month when his son was due to compete at the Italian Open.

The world number 26 pulled out of the competition in Italy to return home. His mother, sister, and fiance all came to join him in Geneva as he prepared for the French Open.

Johnson added: "Physically I'm OK, emotionally I'm a mess.

"I just know this is what he always taught me to be - a fighter, be a competitor, day in day out, so that's what I'm going to do. That's the only thing I can do."

In the fiercely contested game, frustrations got the better of Johnson’s opponent, as the Croatian repeatedly smashed his racket into the floor after losing the fourth set.

You can watch the emotional interview in the video below.

"That's quite logical, I think, I was on the court for four hours. And it's not something which should be my excuse, but I got mad.

"I think everyone gets mad from time to time. Maybe I didn't show it in the right way but I made a mistake, but that's it."

Johnson will face a tougher test in the third round against sixth seed Dominic Thiem.