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SURPRISE, Ariz. (AP) – Slugger Prince Fielder returned to the Rangers’ spring training on Friday and was inserted into the lineup as Texas’ designated hitter against Milwaukee after being tested earlier this week for a sleep disorder.

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Fielder, who missed three games, went to the Dallas-Fort Worth area on Wednesday for tests, which determined he had sleep apnea, a potentially life-threatening ailment in which breathing stops and starts during sleep. Fielder had complained about having trouble getting rest.

He said the exams detected that he stopped breathing 39 times per hour, while 30 is considered dangerous. Fielder will now use a breathing mask during sleep.

“My wife told me I always snored loudly and stopped breathing in my sleep,” Fielder said. “You don’t feel it as much when you’re young, but as you get older, it affects you more. I wasn’t panicking, but I wanted to make sure.

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“I felt like I was sleeping long, but I didn’t feel rested. That was my concern, trying to figure out what was wrong with that. Now that I know, I can sleep through the night. My wife can sleep, too, since I don’t snore.”

Fielder was the 2015 American League Comeback Player of the Year, hitting .305 with 23 home runs, 28 doubles and 98 RBIs. He missed most of the 2014 season, hitting three home runs in 42 games, and needed season-ending neck surgery.

Fielder expects a better night’s sleep will lead to better performance on the field.

“Believe it,” he told reporters.

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