Frankie Montas, who is coming off another disappointing loss on Friday night, was sent for an MRI on his right shoulder Saturday afternoon. The right-hander, who has a 6.35 ERA with the Yankees in eight starts, has been a disappointment since the Bombers acquired him from the A’s at the trade deadline. Montas told the YES Network that he woke up with a little bit of an “impingement” on Friday. Montas missed from July 3-21 with a shoulder issue while with the A’s. He returned to make two starts with Oakland before the Yankees traded for him. The 29-year-old, who is under team control next year …