Justin Masterson

Justin Masterson will miss his scheduled start against Seattle on Sunday because of a sore right knee.

(Tony Dejak/Asscoiated Press)

PHOENIX, Ariz. – Manager Terry Francona said earlier this year that there's not a pitcher in the big leagues who doesn't have something "going on" that might stop a non-athlete from throwing a baseball for a living.

Francona was talking about pitchers' arms. He did not mention knees, but he could have regarding Justin Masterson.

Masterson, the Indians' No. 1 starter, will miss his scheduled start Sunday at Safeco Field because of soreness in his right knee. He said he's been dealing with it since his second start of the season. That would be 16 starts ago.

"It started after my second start of the season," said Masterson, the Indians' ace, who hasn't pitched like an ace this year.

Has that been the reason Masterson's ERA has risen to 5.03, higher than any starter on the staff? Or why his velocity has dropped so dramatically?

"I don't know," said Masterson, after the Indians' 6-1 victory over Arizona on Wednesday night. "It's just been a little nagging. Maybe it's taken (away) a little of the power and consistency?"

Francona said before Thursday's game that Masterson will be shut down for the next two days before testing the knee by throwing a bullpen session this weekend in Seattle.

"I'll get pushed back a couple of days and then come back firing," said Masterson. "Technically, I'll miss that start Sunday, but I'll probably pitch a couple of days after that."

The Indians end their three-game series against the Mariners on Sunday. They open a three-game series against the Dodgers on Monday at Dodger Stadium. If Masterson gets through his bullpen session without his knee barking too loudly, he could start Tuesday or Wednesday's game.

"It's been pretty nagging and all that kind of stuff," said Masterson of his sore knee. "As you go through it you're wondering what exactly is happening here.

"This might be a good time to do this. We have the ability to throw someone else in there and push me back a couple of days. We might as well take the opportunity now to give it a little rest. I feel like that should help us be able to creep back up to the top."

Masterson, who has walked 50 batters in 93 innings, said he has not had an MRI on the knee.

"I don't think it's that serious," said Masterson. "It's caused by how I throw. I turn my right knee to the inside when I throw. It's nothing too crazy. I just think a couple of extra days will be nice for it."

The Indians will have to recall a starter from Class AAA Columbus to make Masterson's start on Sunday. Lefty T.J. House is a possibility.