Adam Schefter breaks down Kyler Murray's expressing his full commitment to the NFL, saying he expects Murray to be drafted in the first round. (1:47)

Kyler Murray has tweeted that he is "fully committing my life and time to becoming an NFL quarterback," answering the question of whether he will choose football or baseball.

The 2018 Heisman Trophy winner posted a statement on his Twitter account Monday, four days before he was scheduled to report to spring training with the Oakland Athletics.

Murray did not mention baseball or the A's in his statement. Murray will return $1.29 million of the $1.5 million signing bonus the A's gave him last year, a source told ESPN's Jeff Passan. Murray forfeits the remaining $3.16 million, due March 1. The A's will put him on the restricted list and retain Murray's rights, but they won't get a compensatory draft pick.

Murray has chosen Erik Burkhardt of SSG as the agent to represent him in the NFL, sources told ESPN's Adam Schefter. Scott Boras represented Murray in baseball.

Burkhardt also represents Arizona Cardinals head coach Kliff Kingsbury, who said last fall when he was the coach at Texas Tech that he would take Murray if he had the No. 1 overall pick.

"Moving forward, I am firmly and fully committing my life and time to becoming an NFL quarterback," Murray wrote. "Football has been my love and passion my entire life. I was raised to play QB, and I very much look forward to dedicating 100% of myself to being the best QB possible and winning NFL championships. I have started an extensive training program to further prepare myself for upcoming NFL workouts and interviews. I eagerly await the opportunity to continue to prove to NFL decision makers that I am the franchise QB in this draft."

The A's drafted Murray ninth overall last June and he agreed to a minor league contract that included a $4.66 million signing bonus.

"We took the best athlete on the board and what we thought was probably the best baseball player on the board too," A's general manager David Forst said Monday. "... The process was right and I think [A's president of baseball operations] Billy [Beane] told you guys this morning we don't regret the pick at all."

A's manager Bob Melvin said Monday that Murray picking football wasn't "a shock to me."

"We still have the rights to him but it looks to me he is going to have a nice little football career. We are going to be rooting for him," he said.

ESPN's draft experts, Mel Kiper and Todd McShay, both project Murray as a first-round pick. Kiper says, "He's unbelievably athletic and one of the best dual-threat quarterbacks I've ever seen. He can make every throw, and he does it with timing, touch and poise. He could be a really good NFL quarterback."

No player has ever been a first-round pick in both the NFL and MLB drafts, according to the Elias Sports Bureau.

In his latest mock draft, McShay has Murray going No. 13 overall to the Miami Dolphins.

"Yes, the risk is apparent -- Murray is undersized at 5-foot-10 and still hasn't decided on his baseball career," McShay wrote. "But he has an electric arm and some of the best athleticism I've seen at the position in years."

Murray is No. 8 on Kiper's board, released last week.

At Oklahoma, Murray passed for 4,361 yards and 42 touchdowns while posting the highest QBR (95.8) since ESPN began tracking the statistic in 2004. In addition, Murray became the first player in FBS history to average at least 300 yards passing and 60 yards rushing per game.

Murray joined Clemson's Deshaun Watson as the only FBS quarterbacks to pass for 4,000 yards and rush for another 1,000 in the same season. And he surpassed Baker Mayfield's FBS passing efficiency record set in 2017.

ESPN's Jake Trotter contributed to this report.