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4/18/2014 1:47 P.M. ET

Arrieta nearing return with rehab start on tap

CHICAGO -- Jake Arrieta may be one start away from getting back to the big leagues.

The Cubs right-hander will make at least one more rehab start with Triple-A Iowa early next week, and he could then be ready to start for the big league team. Arrieta had tightness in his right shoulder when Spring Training began, and he did not pitch in any Cactus League games.

He has made three rehab starts for Double-A Tennessee, giving up one earned run on six hits and four walks over 12 1/3 innings. In his last outing on Wednesday, Arrieta went 5 2/3 innings.

Arrieta was in Chicago on Friday to throw a side session for Chris Bosio, so the pitching coach could evaluate the progress.

The Cubs acquired Arrieta last July from the Orioles in the Scott Feldman deal, and he went 4-2 with a 3.66 ERA in nine starts.

'Next chapter' begins for McDonald with Cubs

CHICAGO -- When Darnell McDonald reported to the Cubs' Spring Training camp in February, he was fighting for a spot on the Opening Day roster. The outfielder never expected he'd finish with a new job as a baseball operations assistant.

"When you're playing, you never think it's going to end," McDonald said in a phone interview. "I never thought I'd be doing something like this."

At the end of spring, McDonald, 35, met with Cubs president of baseball operations Theo Epstein, who said there wasn't a fit on the roster because the club wanted some of the young outfielders to play at Triple-A Iowa.

"I felt it was time to start the next chapter," McDonald said. "Theo told me they didn't have a job for me [as a player]. I didn't want to go anywhere else. He said he wanted me to be a part of what they're doing, and for me, it was a no-brainer to stay in the game of baseball. I love this game, and everything I have is because of baseball. To have the opportunity to learn from some of the smartest baseball minds in the game and people who are passionate about baseball, it made it easy for me to make the transition."

McDonald announced his retirement as a player after 16 professional seasons, including the last year with the Cubs' organization. In his new job, McDonald will contribute to all elements within the club's player development and amateur scouting departments. He'll visit all of the club's affiliates and work with the Minor League players, plus do some scouting. McDonald also will attend instructional league and serve as an extra coach.

"I want to help guys get to the big leagues," he said. "I want to help these guys bring a championship to Chicago."

McDonald joked the toughest part may be trying to find some khaki slacks, so he can dress the part in the Cubs' front office.

"I want to learn everything," McDonald said. "I'm looking forward to the challenge. I told Theo the same way I developed my skills playing baseball, I want to learn on the other side."

Was it hard to retire as a player?

"It wasn't that hard," McDonald said, laughing. "You go out and leave everything on the field. I have no regrets about anything."

Renteria wants Cubs to 'stay relaxed' on offense

CHICAGO -- Entering Friday's game against the Reds, the Cubs ranked 14th in the National League in runs scored, and had been held scoreless in their last 18 innings. What's a manager to do?

"Maybe we've become a little anxious in our approach at the plate and not putting ourselves in a position or frame of mind that the pitcher is on the ropes," Rick Renteria said Friday about the Cubs players. "I want these guys to stay relaxed. I think when they come to the ballpark, I went them to feel comfortable in their element. There's no reason for us as coaches to put them in a state of panic.

"They're as frustrated as everybody else," Renteria said. "The important thing is to step away from the frustration and just regroup and put their approaches back into play and maximize run production."

That hasn't been easy this season. The Cubs are batting .195 with runners in scoring position (only the Padres and D-backs are worse in the NL).

"I will be the last one to panic," Renteria said. "Offenses come and go. What I'm really happy with is our pitching has been doing a great job for us, especially our starting pitching."

Chicago's starting pitchers rank eighth in the NL, with a collective 3.98 ERA.

Renteria said he hopes his players learn from their early struggles, and he added it's imperative he and the coaching staff stay calm.

"There are no guarantees -- you can have the best approach in the world and you can square up a ball and still have someone make a play," he said. "The reality is the calmer they become in the box in key situations, the better they'll be. It's incumbent on us to make sure they see the calm in us, because if they see the panic in us, it's a bigger problem."

Carrie Muskat is a reporter for MLB.com. She writes a blog, Muskat Ramblings, and you can follow her on Twitter @CarrieMuskat. This story was not subject to the approval of Major League Baseball or its clubs.