CHICAGO -- Cubs right-hander Jacob Arrieta is ready to pitch whenever he is asked in the upcoming National League Division Series presented by T-Mobile against the Nationals.
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But Arrieta won't be ready to take the mound as scheduled on Sunday when the Cubs wrap up the regular season at Wrigley Field against the Reds.
Arrieta, who missed 2 1/2 weeks with a sore right hamstring, said on Friday that rather than pitch Sunday, he will throw a simulated game to give him more time to move closer to 100 percent.
"He's not pitching on Sunday," manager Joe Maddon said. "He's not. That's official."
The Cubs announced after Friday's 5-4 come-from-behind victory over the Reds that Mike Montgomery will start in Arrieta's place.
"It's good to get a couple extra days off, especially with the situation that we're in -- we're already in the playoffs," Arrieta said before Friday's game.
Arrieta said the only time his hamstring bothers him is when he is working at full effort. Arrieta and Maddon said that the extra time off is merely a precaution to allow Arrieta to be ready for the postseason.
Maddon said Arrieta will likely throw a simulated game on Wednesday next week.

Maddon added that the extra time will likely push Arrieta back in the Cubs' starting rotation to at least the No. 3 slot against the Nats. The manager won't set his rotation until early next week, but Arrieta -- who pitched just three innings on Tuesday against the Cardinals -- said he isn't concerned with which slot he fills as Chicago begins its defense of last season's World Series championship.
"When my time comes, I'll be ready -- regardless of when that is," Arrieta said. "Whenever they want me to pitch -- if it's Game 1, 2, 3 -- it doesn't matter. I'm more than capable."
Arrieta (14-10) had won four straight decisions before losing two of his three September starts. But Maddon believes that the extra time off heading into the postseason could benefit Arrieta, --and in turn, the Cubs.
"A real healthy Jake pitching like he can is very important to us -- there's no question about that," Maddon said. "It's just moving forward right now -- that was a significant injury. We're trying to get him back to being a more normal Jake.
"Listen, he could be very large for us in the next series coming up."
The right-hander said that he is not concerned about arm strength or anything beyond the hamstring being fully healed.
Arrieta said he is able to control his effort and that he's not attempting to "throw a ball through a brick wall." But especially with the rest he could get, he has no doubt he will be fully prepared to face the Nats.
"I don't need to be any more crisp because that's there," Arrieta said.