Meet Matija Pecotic: A real-estate investor who counts Bill Ackman as a mentor - and is now a breakout tennis star on the pro circuit

• A 33-year-old real-estate investor has become a tennis star after beating a former top-10 player.
• Matija Pecotic works full time, but plans to play in 25 professional tennis events this year.

A real-estate investor in his 30s, who counts Bill Ackman as a mentor, has become a breakout tennis star after beating a former top-10 player at a Florida tournament in February.

Matija Pecotic, a Princeton graduate with a Harvard MBA, works full time as a director at Wexford Real Estate Investors in Palm Beach, Florida.

He left work early to play top US prospect Jack Sock on Valentine's Day. Following his shock victory, Pecotic plans to compete in about 25 tennis events this year without giving up his job, he told The Wall Street Journal in a recent interview.

Pecotic — a Croatian born in Serbia — turned pro in 2014. He was threatening to break into the world's top 200 players before illness sidelined him.

Ackman, the billionaire boss of Pershing Square, became one of Pecotic's first sponsors after watching him train with the Serbian world number one, Novak Djokovic.

"You don't belong in the office just yet," Djokovic joked on Instagram after Pecotic's surprise win over Sock.

Pecotic, 33, quickly grew interested in a business career after moving to the US. "I recognized the finitude of a tennis life," he told WSJ.

"Being mentored by Bill Ackman continued to influence that hunger," Pecotic said. "I learned everything I could from him. He has that famous reading list that he gives to his incoming analysts. I read all those books."

Ackman's reading list includes "The Warren Buffett Way" by Robert Hagstrom, "Beating the Street" by Peter Lynch, and "The Intelligent Investor" by Benjamin Graham.

The moonlighting tennis star scours match tapes and other information sources to spot his opponents' weaknesses and refine his own game. He drew a parallel to high-frequency day traders parsing vast amounts of data.

"In our world, we are all about information, put the emotions aside – analytics, analytics, analytics," he said.