Yankees manager Aaron Boone told reporters Saturday that Severino had another MRI after he was shut down with soreness. He added the right-hander's strained lat is 90 percent healed, but he won't throw off a mount until it's back to 100 percent.
Both pitchers have been sidelined since spring training.
Severino first dealt with inflammation in his right shoulder in early March. The ace starter was then shut down for six weeks after being diagnosed with a strained lat, as he experienced discomfort when he started throwing from 130 feet.
No return date has been established, though Yankees general manager Brian Cashman told Jim Bowden on MLB Network Radio in May the two-time All-Star would not be back "until after the All-Star break."
Betances was diagnosed with a right shoulder impingement amid concerns about the velocity of his fastball. The 31-year-old averaged 89 mph with his heater during a March 17 appearance against the Philadelphia Phillies.
Per FanGraphs, the four-time All-Star reliever has averaged 97.3 mph with his fastball during his MLB career.
The Yankees haven't had any problems without two of their best pitchers. They own the American League's best record at 52-28 entering play Saturday.