The Chicago Cubs used a sixth starting pitcher earlier this month, and they’re going to use another on Sunday Night Baseball.

For the nationally televised game against the Seattle Mariners at Wrigley Field, the Cubs will select the contract of veteran left-hander Brian Matusz from Class AAA Iowa. They will option relief pitcher Justin Grimm to Iowa to make room for Matusz.

The idea is to give the top five pitchers in the rotation a bit of a breather. Kyle Hendricks, originally scheduled to start Sunday, will be moved back to Monday’s series opener against the Miami Marlins.

On July 6, the Cubs gave a spot start to Adam Warren against the Cincinnati Reds. Warren was traded to the New York Yankees this past week in the deal that brought reliever Aroldis Chapman to Chicago.

“You almost always have to make your best guess,” Maddon said of when to use a spot starter. “You see how well our guys have been doing since the start of the second half. We knew they needed a rest. We gave it to them. Coming out of (the all-star break) we just think it’s prudent to be proactive with the moment, not to wait.

“So many times you push and push and push and eventually, the rest is absolutely necessary. Prior to it being absolutely necessary, it’s a hard sell sometimes to the rest of the group. But we try to lay it out to guys. You look at the dates and who you’re playing and left-handedness, right-handedness, all these different components, who’s done well, who matches up better against a particular group. So you just try to roll out your best plan in advance.”

The 29-year-old Matusz spent his entire major-league career with the Baltimore Orioles, beginning in 2009. The Orioles traded him to the Braves in May, and the Braves released him on June 1. He did not pitch for Atlanta. The Cubs signed him as a free agent June 14.

Matusz has made 2 starts at Iowa, going 0-0 with a 1.93 ERA. He has not started a major-league game until 2012.

Grimm is 0-0 with a 4.72 ERA in 45 games.

A partial rest for Rizzo:

First baseman Anthony Rizzo got most of Saturday’s 4-1 loss to the Mariners off. He did not start, but he did strike out as a pinch hitter in the eighth inning. He stayed in the game at first base.

Joe Maddon is trying to get rest for all his regulars as the season enters its final two months.

“He’s really been needing a day,” Maddon said. “It just turned out really well for today. Day game and then a night game tomorrow, so it gives him a little bit extended time to rest.

“We rely on him so heavily all the time. It was just the right thing to do today. I don’t want to wait until a guy gets hurt to need a day off. I’d rather be proactive with that. I put out the feelers yesterday to ask around who’s going to be needing a day. For today, it was absolutely the right thing to do with Riz.”