"He had some injuries last year, but the sky's the limit," Darnell said. "He has the chance to be one of the best pitchers in the game."
The McDonalds are together in Cubs camp. James was one of two pitchers who formally signed Thursday, joining Jason Hammel. McDonald inked a one-year, $1 million contract; Hammel signed a one-year, $6 million deal. More on Hammel later.
Darnell, 35, is a non-roster invitee, and battling for a spot on the bench. It would be easy for Darnell to say nothing but nice things about James because they are family.
"That's the good thing about family is they won't say everything you want to hear, but you can tell them everything you need to hear," Darnell said. "I'm glad he's over here. This is the time in his career that he can go up to that next level."
James, 29, had a tough time last season with the Pirates. He was limited to six games because of shoulder issues, and he posted a 2-2 record and 5.76 ERA. Pittsburgh designated him for assignment in September and outrighted him to Triple-A Indianapolis, but McDonald refused the assignment, electing free agency.
"I came out here right after the season ended," James said. "I was disappointed in the season. I sat down and talked to my agent, and he told me the same thing basically that Darnell told me -- 'Hey, it's time for you to put in work, prepare yourself better this offseason.' He gave me options on what I needed to do. I decided to come down here, move my family to Arizona and started working out the first week in October, five days a week."
He did the work at Pro Advantage training in Gilbert, Ariz. There was a lot of emphasis on improving his shoulder strength.
"I gradually started feeling better, better, better," James said. "By the time I started throwing, I was like, 'This is how I remember feeling.' I threw a couple bullpens. I guess the Cubs liked what they saw. I like the opportunity here; I like the group of guys here, the chance to play with my family. I feel this is the best place for me."
There's no nonsense with the McDonalds. James knows Darnell will be honest. There is some friendly razzing. Darnell has two at-bats against his cousin, and he is 0-for-2 with one strikeout.
"There was a cheap shot that he hit back to me, and I threw it away," James said, laughing.
Hammel does not have a family tie to the Cubs, but he did ask Scott Feldman what it was like to pitch at Wrigley Field. Feldman signed with the team last year and was dealt at the Trade Deadline to the Orioles.
"Play the wind, I guess," Hammel said of the advice from Feldman. "He was like, 'It's 50-50. It's either going to blow straight out, or it's going to blow straight in, and hopefully you pitch on the straight in days.'"
Hammel has been to Wrigley four times but never pitched there.
"[Feldman] said, 'Jason, you want to really think hard about Chicago,'" Hammel said about going into free agency. "[He said], 'It's a great organization, top-notch front office, and the guys are great, too. Very good baseball environment.'"
However, Feldman was flipped at the Trade Deadline for prospects. Does Hammel see that happening to him?
"I'm not even thinking about that," he said. "The offseason is for the business side of baseball. Now it's time to go win ballgames. I think I can speak for every ballplayer; they want to stay in one place for a long time. I want to go out and do my job and pitch well and let the cards fall where they may."
Thursday was the first day Cubs pitchers and catchers worked out, and McDonald threw a side session along with Jeff Samardzija, Travis Wood, James Russell, Wesley Wright and others. This is the time when players bond together, and get to know their second "family."
The McDonalds have an edge in that they already have a bond.
"I tell him the good and the bad," Darnell said of his conversations with James. "That's the good thing about family."
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.