BOSTON — Before acquiring Martin Prado from the Diamondbacks on Thursday, the Yankees inquired about the Mariners’ Dustin Ackley.

Nevertheless, when Seattle asked for minor league right-hander Bryan Mitchell, the discussions essentially ended because the Yankees view the 23-year-old right-hander as a rotation candidate either this year or next.

Ackley, 26, was the second pick of the 2009 draft out of the University of North Carolina and has moved around from second base, to first base, left field and center field. He has played in 85 games this year in left and been the DH in seven others, batting .253 with five homers and 36 RBIs.

Mitchell, who scouts says has more velocity than Shane Greene, hitting 95 mph, is at Triple-A Scranton/Wilkes-Barre after starting the season at Double-A Trenton. In a combined 18 games, he is 4-6 with a 4.32 ERA. In 81¹/₃ innings he has fanned 75 and walked 37. Mitchell was a 16th-round pick in the 2009 draft out of a North Carolina high school.

Masahiro Tanaka was examined by Yankees team doctor Chris Ahmad Friday in New York.

“He gets looked at regularly and every day there is no problem is a good day,’’ general manager Brian Cashman said before the Yankees’ 4-3 loss to the Red Sox at Fenway Park.

Monday is the three-week anniversary of Tanaka receiving a PRP shot for his torn right ulnar collateral ligament and the Yankees said at the time that would be a milestone.

“Obviously when we get home [Monday] we’ll see what the doctor says is the next plan for him,’’ manager Joe Girardi said. “But I know he feels much, much better.’’

Tanaka and the Yankees are hoping a rehabilitation program will enable Tanaka to avoid Tommy John surgery, which would put him out for between 12 and 18 months.

Because Prado — who wasn’t in Friday night’s lineup because he wasn’t slated to arrive at Fenway Park until close to 6 p.m. for the 7 p.m. game — can play multiple infield and outfield positions, Girardi is going with 13 pitchers for the time being.

Prado pinch-hit for Ichiro Suzuki in the seventh and stayed in right field . He went 0-for-2.

That meant when right-handed reliever Esmil Rogers was added to the roster Friday night the Yankees didn’t send a pitcher out.

That left Girardi with three bench players.

The 40-year-old Ichiro, who went 1-for-2, is in a 4-for-24 (.167) slump and his decline forced the Yankees to acquire Prado.

Michael Pineda is scheduled to start for SWB Sunday. That will start the clock on the right-hander’s 30-day rehab assignment. The Yankees are encouraged by what Pineda has done in two workouts as he recovers from a terres major muscle problem in the back on the right side. He is scheduled to throw 65 pitches.

Girardi used his 20th challenge of the season in the sixth inning when Jacoby Ellsbury was initially called out attempting to steal second. The call was over-turned after the review process to on minute and 46 seconds. … Derek

Jeter’s eighth-inning homer was his 14th homer in Fenway. It’s the second-highest total for Jeter on the road. He has 15 in Camden Yards.

To make room for the three new players the Yankees designated Brian Roberts for assignment and optioned Zelous Wheeler and Zoilo Almonte to SWB.

While the Yankees added Prado and Stephen Drew to their team Thursday the Red Sox acquired outfielder Yoenis Cespedes and a draft pick from the A’s, outfielder/first baseman Allen Craig, pitcher Joe Kelly from the Cardinals, infielder Kelly Johnson from the Yankees and minor league pitcher Eduardo Rodriguez from the Orioles.

Pitcher Jon Lester and outfielder Jonny Gomes went to the A’s, pitcher John Lackey went to the Cardinals and lefty reliever Andrew Miller went to Baltimore.

“I think they are trying to improve their club as well,’’ Girardi said of the AL East cellar dwellers. “They have had to go through some things this year and maybe they weren’t where they thought they would be. They made some moves to try and help their club. It’s probably not something you would expect on April 1 but it did and we will see what happens.’’