CHICAGO -- The Cubs will go with a six-man rotation prior to the All-Star break, but they first need to prep the extra starter, Adam Warren.
On Tuesday, the Cubs optioned Warren to Triple-A Iowa, where he was expected to make two starts before rejoining the big league team for one start before the break. The Cubs are in a stretch of 24 straight games before the All-Star Game presented by MasterCard, which will be played July 12 in San Diego.
"This stretch we're on now, with starters not getting any kind of a blow, we thought it was the most optimum moment to attempt to do something like this, so we are," Cubs manager Joe Maddon said. "[Warren] is going to definitely start pre-break, and I don't know what will happen post-break. He was very receptive."
Warren threw 51 pitches in two innings of relief on Sunday against the Pirates. He made 17 starts last season with the Yankees, and has made 20 starts in his career.
Maddon was not ready to reveal when Warren, 28, was penciled into the Cubs rotation. The right-hander will make at least two starts at Iowa.
The Cubs also placed left-handed reliever Clayton Richard on the 15-day disabled list with a blister on his left middle finger. To fill the two spots in the bullpen, the Cubs recalled right-hander Spencer Patton and selected the contract of lefty Gerardo Concepcion from Iowa.
Richard, 32, has given up two earned runs over 3 1/3 innings in his last six games, and appeared in 22 games this season. He also has a problem with the nail on his left middle finger, so the time off will help heal that.
"His finger is pretty nasty looking, so it'll be good to give him a break," Maddon said.
Patton, 28, had a 1.04 ERA in 26 relief appearances with Iowa, and walked nine while striking out 42 over 26 innings. He broke into the big leagues with the Rangers in 2014.
Concepcion immaculate in debut
It's taken Concepcion a long time to get to Wrigley Field, and on Tuesday night, the lefty finally made his Major League debut. Concepcion, whom the Cubs signed in March 2012 to a five-year, $6 million deal, pitched 1 1/3 innings against the Cardinals, and struck out two of the four batters he faced.

Last season, he opened at Class A Myrtle Beach and finished at Double-A Tennessee, where he compiled an 8.24 ERA in 31 games. But this year, he's a different pitcher. Concepcion did not give up a run over 17 2/3 innings at Tennessee, and at Iowa, he was charged with five earned runs over 17 1/3 innings.
"I was frustrated when everything was going wrong," Concepcion said through coach Henry Blanco.
He spent the offseason working on throwing strikes, and that's exactly what he did in his debut. Concepcion, 24, struck out the first batter he faced, Brandon Moss, to end the sixth on an 92 mph fastball. Did he get the ball from that first big league strikeout?
"He will get it," Blanco said.
Concepcion is the first Cuban-born pitcher to make his debut with the Cubs since Oscar Zamora in 1974.