Brian Johnson works his way back in Pawtucket

Any time a big league starter leaves a game because of injury, attention turns to potential alternatives, starting with the pitcher on the mound that day in Triple A. So it was that Eduardo Rodriguez’s exit from Tuesday’s game in Baltimore directed attention toward the strong work being submitted by lefthander Brian Johnson in his return to Triple A.

Rodriguez was four innings into a no-hit bid when he left with a hamstring injury. (It appears he won’t miss a start.) Johnson, likewise, had cruised through four no-hit innings of his own against Lehigh Valley, en route to a line of seven innings, one run on four hits, no walks, and two strikeouts.

In late July, Johnson (5-5 with a 3.82 ERA this year in Pawtucket) struggled in his first start back since taking a leave in mid-May to seek treatment for anxiety. But since then, he has carved the strike zone with a familiar four-pitch mix (fastball, curveball, slider/cutter, changeup), resulting in four straight starts of at least six innings. He has a 1.78 ERA with 15 strikeouts and four walks in 25⅓ innings during that time.

“There’s a presence on the mound that he’s reestablished,” said Pawtucket pitching coach Bob Kipper, who has worked with Johnson since 2014 in Double A Portland. “What made Brian Johnson special was he was upbeat, there was control, there was an attacking of the strike zone with a mix that led to a level of unpredictability that made hitters uncomfortable.

“They couldn’t get comfortable to an area of the strike zone or a pitch. It was like, ‘Game on — anything can happen.’

“He’s on his way to kind of reestablishing the pace in which he pitches, the strike-throwing ability, the pitch mix.”

While Johnson is once again showing control, tempo, feel, and unpredictability, he remains something of an unfinished product, likely because of the lengthy layoff that has him trying to rebuild arm strength. At his best in 2014, Johnson typically pitched at 89-91 or 92 m.p.h., sometimes bumping 93. Since his return to Pawtucket, he’s more often sat at 87-90 m.p.h., while working his way back toward the swing-and-miss finish to his curveball.

“In some respects, it’s much like another spring training all over,” said Kipper. “There’s a crispness to his stuff now, but it’s probably a tick down compared to 2014.

“That’s not concerning to me. What he’s going through is a process. You’re conditioning your body, conditioning your arm to maximize what you’re capable of doing. But he’s been fun to watch here.”

Johnson is putting himself close to a position where, if the Red Sox need a depth starter, he’d be a consideration. At the same time, the gap between where he is and where he could end up may argue in favor of caution.

“I think he needs more time,” said Kipper. “He needs to start more baseball games here. He needs to continue to get comfortable.

“He’s certainly well on his way. I just think, I don’t feel that there’s a rush to get him there. What he’s been through, we have to take that into consideration. We have to allow this guy to get really, really comfortable again in his game.”

That is far from an indictment of how far he’s come since the beginning of the year.

“I think this has a chance to be a really neat story, a guy who has battled through what he’s gone through this year,” said Kipper.

“He has really shown some courage here in taking the necessary steps to put himself back on track. It’s a credit to the organization that supported him, but more importantly, it’s a credit to him.”

No rush on Moncada

Since he suffered an ankle injury on a hard slide Aug. 5, Yoan Moncada had played just twice for Portland entering Thursday. He had resumed pregame work in the field.

Still, when he does return, the Sox are betraying little sense that he needs to be rushed out of Double A. The organization believes he’s being challenged by the level of competition there, at a time when the 21-year-old is learning a new position (third base) and hitting .230 with a .299 OBP and .393 slugging mark (along with 22 strikeouts in 67 plate appearances) over his last 15 games, down from .329/.415/.683 in his first 21 contests for Portland.

“[Andrew Benintendi] had a little bit of a different situation [in Portland],” said farm director Ben Crockett. “He was challenged early and really took a step forward towards the end.

“[Moncada] has shown some flashes of brilliance here, and there have been times when he’s been challenged by good opponents that are attacking him or where he’s been challenged on the defensive side. I think that continues to be the case.

“Everyone is going to be challenged by any level they’re at to some degree, but I think this has been a good spot for him. He came out really hot, swung the bat really well, and then it challenged him.”

Cosart mixing it up

Reliever Jake Cosart is off to an overpowering start in High A Salem. In his first three games, opponents are 1 for 25 with one walk and 15 strikeouts against the 22-year-old in 7⅔ shutout innings. At times in Greenville, he blew away opponents chiefly with a fastball that reached triple digits. But in Salem, he has shown the ability to get swings and misses with his curveball and splitter. “Both pitches have their moments and show pretty good potential,” said Crockett . . . At Greenville, a pair of top power-hitting prospects are mired in lengthy struggles. First baseman Josh Ockimey is hitting .157/.291/.320 in 42 games since the All-Star break. Third baseman Michael Chavis is hitting .224/.307/.356 with five homers in 57 games since returning from an early-season thumb injury . . . Lowell lefthander Darwinzon Hernandez, who led the Dominican Summer League last year with a 1.10 ERA, ranks second in the New York-Penn League with 11.4 strikeouts per nine innings. The 19-year-old is 3-4 with a 3.41 ERA. In his last two starts, he has punched out 17 batters in 10 innings.