SEATTLE -- Unable to land a left fielder at the trade deadline, the Red Sox have decided to promote from within -- Andrew Benintendi, who had been at Portland, will join the Red Sox here tomorrow, a source confirmed.

Benintendi, 22, the Red Sox' first-round draft choice out of the University of Arkansas 14 months ago, will make the unusual -- but not unprecedented -- jump from Double A to the big leagues.

The outfielder hit two homers Sunday and has a slash line of .295/.357/.515 in 63 games with the Sea Dogs. He had eight homers and 44 RBI.

Benintendi played center field for most of the season, but in anticipation of a late-season call-up to the big leagues, began to play left field a little more than a week ago at Portland.

The Sox have been struggling to get some offense out of left field. Brock Holt is mired in a slump and the Sox have been getting little out of Bryce Brentz of late.

Boston attempted to obtain Carlos Beltran from the Yankees on the day of the trade deadline Monday, but felt the price too high. Beltran ultimately was traded to Texas.

John Farrell said the left-handed hitting Benintendi won't start Tuesday against Mariners' left-hander Wade LeBlanc, but will likely start Wednesday night in Seattle against right-hander Hisashi Iwakuma.

"There's been a lot of discussion on [calling him up] the last few days,'' said Dave Dombrowski after the Red Sox edged Seattle 2-1 Monday night. "We spent a lot of time on the phone with our Player Development people. It really came down to, we looked at some possible alternatives to help us in left field [via trade]. We thought some of them were good choices, but we also thought the cost for some of those were quite high.

"We also weighed that versus the availability [of Benintendi]. Our people kept coming up and saying, 'We think he could play at the big league level; we think he's ready.' We don't look for him to hit in the middle of the lineup, like he will eventually. But he's a well-rounded player. He's a good defensive player. He runs the bases well. He has a good arm. We've been working him out in left field.

"It really came down to we feel he can come up here and contribute to the club and help us win. And that's important at this time.'’

Sean McAdam can be followed on Twitter: @Sean_McAdam