Speaking before New York's 14-1 victory over the Boston Red Sox, Boone updated reporters on his team's pitchers, adding that reliever Miguel Castro, who also has shoulder woes, is in line for an MRI and will not throw for four weeks.
But Severino is of primary concern, as the first-place Yankees, who have slowed from their May and June surges, are struggling a bit headed into the All-Star break. They had lost two in a row prior to the Saturday game, and six of 10 before the victory.
Severino, who last pitched Wednesday against the Cincinnati Reds, has right shoulder tightness, and was sent for an MRI after the start.
"After the second inning when I was warming up, it was getting worse. I told myself, before something even bigger happens, stop it right here," he said Wednesday. "Hopefully, it's not something that will take too much time."
Severino, 28, part of an impressive rotation that has the Yankees comfortably atop the American League East, is 5-3 this season in 16 starts. Across 86 innings, he has 95 strikeouts and a 3.45 ERA.
Against the Reds, in a game the Yankees rallied to win in extra innings, Severino allowed four runs on four hits with two walks in just two innings of work. He had lasted six innings in each of his previous three starts.
"We all knew he was struggling a little bit in the second inning," Yankees infielder DJ LeMahieu said. "He was trying to push through it and said he couldn't go anymore, couldn't let it loose. Our starters have been doing such a great job rolling out there every five days. If he goes down, hopefully he doesn't miss too many starts, if any."