"The simple reason is because of innings," said Zduriencik, who added that the Mariners had a plan from the beginning of the year to limit Pineda to between 140 and 150 innings this year.
"Our decision is that we think this is a prized product of ours and a guy we want to protect."
Pineda, 21, had elbow problems throughout 2009, which limited him to 47 1/3 innings for Class A High Desert. But he came into his own this year, starting in Double-A West Tennessee, where he went 8-1 with a 2.22 ERA in 77 innings, and carried it over to Triple-A Tacoma, where he's gone 3-3 with a 4.76 ERA and pitched another 62 2/3 innings. Pineda, whose fastball reaches the upper 90s, has posted 154 strikeouts in 139 1/3 innings and has remained healthy.
The Mariners would like him to stay that way, which is why they're calling it a season.
"We obviously think a lot of him," Zduriencik said. "We think this guy has a chance to be a quality starter at the Major League level, and we think it's going to happen soon.
"So again, there's no issues here -- nothing physically wrong with him at all. It's just strictly an innings issue, and again, we figure the best thing to do for our best future and his best future is to stop it right now.'
Zduriencik said Pineda would stay with his Tacoma teammates through the end of their season and that there is a "chance" that the Mariners will have Pineda up with the big league team in September "for a few days" to experience life in a Major League clubhouse and see some of his former Tacoma teammates.
After that, the Mariners will send Pineda to Arizona until the end of instructional league and then home to the Dominican Republic. Zduriencik said Pineda is slated to return to Arizona in January to be ready for Spring Training in Peoria the following month.
And as for what happens there, Zduriencik said the team is eager to find out. That's because the Mariners view Pineda as having a serious chance to break camp with the Major League team in '11.
"I think he comes into camp next year, I think that should be the mindset that he has," Zduriencik said. "We've seen this guy dominate this year. ... All the earmarks are there that this guy has a chance to have a very, very good future. ... We feel strongly this guy's going to have a great shot to make our club."