Johnson won his two spot starts this season, including a five-hit shutout against the Mariners during his last outing for the Red Sox on May 27 at Fenway Park.
There was some concern that Johnson, the Red Sox's No. 11 prospect, wouldn't be able to pitch on Friday after he left his last start for Pawtucket with cramping in his right hamstring.
"He got through his bullpen fine yesterday," said Red Sox manager John Farrell before Wednesday's game at Yankee Stadium. "He went through a battery of agility tests this morning and earlier today. He passed all those. So he's been notified and will be here to start on Friday. Brian comes to us with a little momentum and confidence after the game against Seattle."
As for Rodriguez, there is still no timetable on his return to action, though he did do some throwing on Wednesday for the first time since suffering his injury in Baltimore last week.
"He threw out to 120 feet of long toss, so that was encouraging," said Farrell. "And just subjectively, the stride length was similar to what he normally has. So those are good signs physically."