Mardy Fish, a former Top-10 tennis player, has encountered his latest setback in an attempt to return to the sport due to a current battle with heart issues, announcing Wednesday that he is pulling out of the U.S. Open.

According to The Associated Press, the U.S. Tennis Association said Fish, 31, said his withdrawal from the tournament was due to "personal reasons." U.S. Open play begins Monday and the draw for this year's Grand Slam tournament is slated for Thursday.

The personal issues stem from complications with his heart.

Fish tweeted the following Wednesday:

Fish spoke earlier this month about the health difficulties that have set him back the last two years.

"I struggled mightily during the U.S. Open last year," Fish said per The Associated Press. "So those sort of post-traumatic experiences that I've had - that I have now - are what I need to get over right now. But it's a process. It's not an easy game. And fitness is as big a part of it as playing, and sometimes that's trouble - spells trouble - for me."

Fish, a Minnesota native now living in Los Angeles, reached a career-best ranking of No. 7 in 2011 but has endured many difficulties since. AP reports that during a match Tuesday against Jarkko Nieminen in North Carolina in a hard-court tournament, Fish had to stop the match in the third set due to heatstroke.

Fish played eight matches on the ATP World Tour this year, posting a 3-5 record, but skipped all of the Grand Slam tournaments. This isn't his first bout with health issues.

Fish was set to face Roger Federer in the fourth round of the U.S. Open last year, but withdrew from the match, citing doctor's orders and health precautions as the reason. Fish also said his heart started racing uncontrollably after a key loss in Florida in March 2012, and doctors had to induce extreme heart palpitations. He didn't return to action until last year's Wimbledon.

According to AP, Smith is ranked No. 173 this week. He has made the quarterfinals on three separate occasions in Grand Slam tournaments in his career, but hasn't advanced any further.