Rotation changes on the horizon for Red Sox

Brian Johnson has made one major league start, allowing four runs over 4⅓ innings against Houston on July 21. Richard Carson/Associated Press

The Red Sox will stick with their current rotation through the weekend, sending out the underachievers who have put together a 4.91 earned run average, the highest among any group of starters in the American League.

But change is finally coming.

Manager John Farrell said Wednesday that lefthander Brian Johnson will be worked into the rotation next week and that another young lefty, Henry Owens, likely will join him.

“All that is on the horizon,” Farrell said.

The Red Sox will start Steven Wright on Thursday followed by Eduardo Rodriguez, Joe Kelly, and Wade Miley against the Tampa Bay Rays.

Monday is a scheduled day off and “we’ve got the ability to adjust,” Farrell said.

Johnson pitched for Triple A Pawtucket on Tuesday and Owens went on Wednesday. They could get one more start in the minors before pitching for the Red Sox in the series in Detroit that starts on Aug. 7.

Farrell said it was unlikely the Sox would pitch either rookie against the Yankees next week.

Johnson has started one game already for the Sox. He faced the Astros on July 21 and allowed four runs on three hits over 4⅓ innings. The 24-year-old is 9-6 with a 2.54 ERA in 17 starts for Pawtucket.

Owens is 3-8 but with a 3.16 ERA in 21 starts for the Paw Sox. He allowed one run over six innings against Norfolk on Wednesday. Owens has given up six earned runs over 25 innings in his last four starts.

Both Johnson and Owens are former first-round picks.

Betts to DL

Center fielder Mookie Betts was placed on the seven-day concussion disabled list, the result of the hard fall he took into the Red Sox bullpen on Tuesday night.

Tests confirmed that Betts suffered a concussion and now his return will be predicated on his passing a test administered by Major League Baseball.

Betts was at Fenway Park Wednesday but was sent home before the game to avoid the bright lights and noise that could aggravate his symptoms.

“The timetable for this is unknown,” Farrell said.

Betts fell over the bullpen wall trying to catch a ball off the bat of Jose Abreu in the sixth inning. He landed hard on his upper back and neck and became dizzy before he could make his way to the dugout.

Betts did not suffer any other injuries, according to Farrell.

The Red Sox have had experience with concussions in recent years. Stephen Drew and David Ross missed time in 2013 and Brock Holt was shut down at the end of last season.

Dr. Micky Collins, an expert at the University of Pittsburgh Medical Center, treated all three players. Betts is not yet scheduled to see Collins.

“If this persists, I would think there would be further exams needed,” Farrell said. “He needs some time to regroup right now.”

Bradley gets a chance

The Red Sox have been stingy with opportunities for Jackie Bradley Jr., this season. But Farrell said Bradley would be the everyday center fielder with Betts out. He was called up on Wednesday.

“This is an opportunity for Jackie and for us to see him in game situations,” Farrell said.

Bradley has hit .305 with an .853 OPS in 71 games for Pawtucket. But until Wednesday, his playing time in the majors consisted of 30 at-bats over 14 games.

Allen Craig, Daniel Nava, Rusney Castillo, and Alejandro De Aza have all logged more innings in the outfield than Bradley, a Gold Glove finalist last season.

Bradley hit .196 for the Sox over 530 plate appearances from 2013-14. He changed his approach at the plate during the winter, shortening his swing. The results have been there in Triple A.

“I’ve felt good at the plate,” Bradley said. “Trying to be consistent.”

Said Farrell: “You can see it in his swing path and his performance in spring training was consistent with closing up some of the holes that emerged last year. It’s been able to be carried over while in Pawtucket and now it’s a matter of being able to do it against major league pitching.”

Pedro, Part 2

The Red Sox retired Pedro Martinez’s No 45 on Tuesday. On Wednesday they repeated portions of the ceremony in Spanish.

Three large Dominican flags hung on the wall in left field. Along with the gifts he received on Tuesday — a seat from the Fenway grandstand and a sculpture of his hands in gold — Martinez received a floral arrangement with his number in roses from De Aza, Alexi Ogando, and Hanley Ramirez, three Dominican players.

Martinez threw out the first pitch with David Ortiz catching.

Guests included Felipe Alou, who managed Martinez in Montreal, and Rafael Avila, the Dodgers scout who signed Martinez.

Janette Marquez, a celebrated Dominican-American opera singer, performed the Dominican National Anthem.

Rutledge arrives

Josh Rutledge, the infielder acquired from the Angels for Shane Victorino, was added to the roster and Jemile Weeks was designated for assignment. Rutledge got into the game in the sixth inning, when third baseman Pablo Sandoval was taken out because of dehydration . . . Righthander reliever Jean Machi, who was claimed off waivers from the San Francisco Giants on Tuesday, is expected to join the team on Thursday . . . When Sandoval hit a home run in the second inning on Tuesday, it was a bit of a Babe Ruth moment. Earlier in the day, Sandoval promised a young girl he met at the Dana-Farber Cancer Institute that he would try to hit a home run for her. “I couldn’t believe it,” Sandoval said. “She was a great kid but I didn’t think I really would hit one. I’m glad I did.” . . . The Boston Pops Jazz Band will headline the Red Sox Foundation’s annual “Picnic in the Park” on Sunday after the game against the Rays. A limited number of tickets are available at redsox.com/picnic . . . Sabermetrics, Scouting, and the Science of Baseball, a weekend seminar for the benefit of the Jimmy Fund, will be Aug. 22-23 at Boston University. Guest speakers from the Red Sox and other teams will be on hand. Go to saberseminar.com for information.