De Leon was placed on the minor-league DL after experiencing minor discomfort in the flexor mass muscle in his forearm last week, the Tampa Bay Times' Marc Topkin reports.
He has been prescribed rest for the ailment, but this is still somewhat concerning. De Leon's innings were going to be limited anyway, after he logged just 103.1 innings in 2016, so this simply alters when he gets his 2017 innings, assuming rest is all he needs to overcome the issue. He will be held back in extended spring training while he builds up strength and will then be activated at Durham.