2014 No. 1 pick Brady Aiken has Tommy John surgery

Brady Aiken, who was selected with the first pick in the 2014 MLB draft by the Houston Astros but did not sign, has undergone Tommy John surgery.

Brady Aiken, who was selected with the first pick in the 2014 MLB draft by the Houston Astros but did not sign, had Tommy John surgery Wednesday, he announced Thursday in an essay for The Players' Tribune.

Aiken, a hard-throwing left-hander from Southern California, did not sign with the Astros after doctors discovered an irregularity with the ulnar collateral ligament in his throwing arm. Aiken's UCL, which was repaired with the surgery Wednesday, was reportedly found to be thinner than normal, but not torn.

• JAFFE: Failure to sign Aiken is black eye for Luhnow, Astros

Aiken was reportedly set to sign for a $6.5 million signing bonus but the deal was called off after the elbow issue was revealed and the Astros changed their offer to about $5 million. Aiken was the first No. 1 pick not to sign since Tim Belcher.

MLB's slotting system values the top overall pick at $7.9 million. The Astros had planned to spend the difference between Aiken's bonus and the $7.9 million slot value on other prospects, including fifth-round pick Jacob Nix. When Aiken did not sign, the Astros' bonus pool shrunk and Nix also went unsigned. 

“I can honestly say I don’t regret not signing,” Aiken wrote in his essay. “It was a very difficult decision, but it also was an informed decision based on circumstances only a few people know the truth about. My family and I planned for all the possible outcomes. We weighed the pros and cons, talked with friends and mentors and doctors whose opinions we value and discussed it over a number of family dinners. This wasn’t a decision we made lightly.”

The players' union filed a grievance against the Astros for trying to manipulate Aiken's signing. 

• REITER: The inside story of how the Astros lost Brady Aiken

Aiken enrolled at IMG Academy in Florida and began pitching for the school's postgraduate team. He left his first start after throwing 12 pitches. Scouts in attendance estimated to Baseball America that there were between 75 and 100 scouts at the game. 

Because Aiken did not sign, the Astros will have the second pick in the 2015 draft. Aiken is eligible for the draft again this year. 

- Dan Gartland