CHICAGO -- Thomas Diamond and Casey Coleman were roommates in Des Moines and teammates on the Triple-A Iowa team. It's only fitting that on Monday, they were called up to the Major Leagues on the same day.

Diamond, 27, and Coleman, 23, were selected by the Cubs and added to the big league roster. There were two openings for pitchers after Ted Lilly was traded Saturday and Carlos Silva was placed on the 15-day disabled list Monday. Diamond will make his debut on Tuesday against the Brewers when he starts in Lilly's spot.

For Coleman, his callup and debut in the Cubs' 18-1 loss was historic. His father, Joe, and his grandfather, Joe, both pitched in the big leagues, and they are the first family in Major League history to have three generations of pitchers in The Show. His father was excited at the news.

"It's big," Coleman said. "A lot of people have asked me about it growing up and all the way high school and college and now. To be able to follow through on it is great."

His father, Joe, played from 1965-79, and made the 1972 All-Star Game with the Tigers. He faced Cubs manager Lou Piniella as well. Casey's grandfather, Joe, had a 10-year Major League career from 1942-55, including an All-Star season in 1948.

Casey never saw either pitch, but his father does rib him a little because Dad was a power pitcher. Casey isn't.

"It's good to live up to the family name -- I'm helping out my dad and grandpa's name," Casey said. "There's been a lot of pressure but it's good pressure and it's fueled me. I've really wanted to do this for a long time."

Coleman was 10-7 with a 4.07 ERA in 20 starts at Iowa. He has struck out 59 in 117 1/3 innings, and was holding batters to a .243 average. He doesn't overpower hitters and has been compared more to Greg Maddux. Not only that, but he's also been tutored by Maddux, now an assistant to Cubs general manager Jim Hendry.

Maddux was with the Iowa team during a trip to Reno, and Coleman said the four-time National League Cy Young Award winner sat in the dugout and talked to him between innings.

"I can really relate to him, being a two-seam guy who doesn't overpower guys," Coleman said. "It was really cool to have insight from him."

On Monday, Coleman was assigned to the bullpen but he also took turns during batting practice with the other pitchers. With Silva sidelined, the Cubs will need another starter. Acting manager Alan Trammell said they would determine the rotation once Lou Piniella returns from Tampa, Fla., where he was attending his uncle's funeral.

The three-game series in Colorado took its toll on the Chicago bullpen.

"If something was to happen to Randy [Wells, Monday's starter] early in the game, you'd see Casey Coleman," Trammell said.

Diamond was 5-4 with a 3.16 ERA in 21 starts for Iowa, striking out 104 in 108 1/3 innings. Opposing teams were hitting .218 off him.

Asked how long he's been waiting for the callup, Diamond said: "Six years."

A first-round Draft pick by the Texas Rangers in 2004, his career was interrupted in March 2007 when he needed Tommy John surgery. The Cubs claimed him off waivers in September 2009. Diamond does have a Cubs connection. Assistant general manager Randy Bush was his coach at the University of New Orleans.

Diamond was pulled after four innings in his last start last Thursday in Albuquerque.

"I didn't know what was going on," Diamond said. "I turned around and saw somebody warming up in the bullpen and thought they were just getting their bullpen work in. They said they had orders to take me out."

That was two days before the non-waiver Trade Deadline. He didn't find out he was coming to the Majors until Saturday. And now that he's in the big league clubhouse?

"It was a lot of hard work and a long time coming," Diamond said.

Diamond inherited Ryan Theriot's locker while Coleman was given Lilly's cubicle. Theriot was dealt to the Dodgers with Lilly on Saturday for Blake Dewitt and two Minor League pitchers, including Kyle Smit, who picked up a win Sunday, pitching 2 2/3 innings of relief for Double-A Tennessee.

"You never know when your day will be," Coleman said. "That's the way it was [Sunday]. It caught me by surprise. There are a bunch of guys down there [at Iowa] who are deserving and can help this team out."

Did Diamond have any butterflies?

"Everybody does," he said. "I've got to go out there and do what I'm capable of doing -- just pitch and throw strikes and give us the best opportunity to win."