JAKUB MENSIK avoided a default after hurling his racket toward a ballboy at the Miami Open.

The 18-year-old was competing in the second round of qualifying against Slovak ace Lukas Klein.

Mensik dropped a tight first set to Klein 8-6 in a tiebreak.

After watching his serve slapped straight back for a winner at 6-7 in the breaker, the Czech teenager was unable to contain his frustration.

As he walked back toward his chair, Mensik launched his racket toward the umpire's chair.

The reckless hurl whistled past a ballboy and luckily did not strike anyone, despite leaving the small crowd in shock.

Mensik ranked No70 in the world, avoided default, and was able to continue the match with a warning.

He went on to lose a similarly tight second set 7-5, thus failing to qualify for the Masters 1000 event - with Klein advancing and drawing Alex Michelsen.

Fans online were left shocked by Mensik's behavior.

One wrote: "That was pretty scary."

While a second asked: "How was this not an automatic default?"

A third commented: "I watched yesterday and wasn’t impressed with how he played, and his attitude towards the game."

Although a fourth countered: "There’s no default for almost hitting someone. Yeah, he shouldn’t throw it but it’s just a warning for racket abuse here."

Another added: "That should be a default regardless."

Mensik has so far enjoyed a breakthrough year on the ATP Tour.

He qualified for the Australian Open in January before beating Denis Shapovalov in round one, eventually having his run ended by Hubert Hurkacz in five grueling sets.

The promising teen then reached the final in Qatar last month, stacking impressive wins against Alejandro Davidovich Fokina, Andy Murray, Andrey Rublev, and Gael Monfils before falling to Karen Khachanov.