D.J. Peterson (Photo by Bill Mitchell)

SEATTLE—General manager Jerry Dipoto wasn’t certain whether first base prospect D.J. Peterson would be claimed in the recent Rule 5 draft, but that’s not why he put the former first-round pick on the Mariners’ 40-man roster.

Despite having never really reached the level of a No. 12 overall pick (2013), the Mariners haven’t given up on Peterson.

“At the end of day we had the (roster) space,” Dipoto said. “He is a first-rounder. He did make progress last year. D.J. has always been able to hit. Where our roster was at, at that point, it made sense for us.”

After hitting .223/.290/.347 in a 2015 spent mostly with Double-A Jackson and ending on the disabled list, Peterson was sent back there for repeat showing. In 73 games, he posted a .271/.340/.466 line with 21 doubles, 11 homers and 43 RBIs.

Peterson earned a promotion to Triple-A Tacoma on June 29. He played in 46 games and posted a .253/.307/.438 line with seven doubles, a triple, eight homers and 35 RBIs. His season was cut short after he fractured a finger on his left hand.

Peterson’s spot on the organizational depth chart has him headed for a likely return to Tacoma. Dan Vogelbach has been slotted for the big league roster, while veteran Danny Valencia will be the righthanded counterpart, brought in to provide depth at first while also playing other positions. With Richie Shaffer designated for assignment, Peterson will see the bulk of the time at first base along with some third base for the Rainiers.

The Mariners have pushed for Peterson to become a more selective hitter while also driving the ball to all parts of the field. There was a feeling that he relied too much on his pull-side power and pitchers had adjusted.

“We don’t think he’s played his best baseball,” Dipoto said. “We wanted to give him an opportunity to stay in the organization and see what he can do.”

MARINADE

• Dipoto confirmed that lefthander Ryan Yarbrough will be invited to big league camp and start at Triple-A Tacoma in 2017. Yarbrough went 12-3, 2.95 in 25 starts at Double-A.

• The Mariners released outfielder/first baseman Stefen Romero to allow him to sign with the Orix Buffaloes in Japan. Romero slashed .304/.364/.541 with 24 doubles, 21 homers and 85 RBIs for Triple-A Tacoma.