MIAMI -- Cubs infielder Tommy La Stella and reliever Clayton Richard joined Triple-A Iowa on Sunday to begin a Minor League rehab assignment. La Stella has been sidelined since June 8 with a right hamstring strain, while Richard went on the disabled list Tuesday with a blister on his left middle finger.
"They're both ready to roll," Cubs manager Joe Maddon said Sunday.
Dexter Fowler, on the DL since June 19 with a right hamstring strain, is making progress but not ready to start a rehab stint yet, and neither is Jorge Soler, who has been sidelined since June 7 with a left hamstring strain.
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Fowler is the key piece the Cubs need to get back.
"With Dexter, that's why I've always said, 'You go, we go,'" Maddon said. "He's been the catalyst at the top of the lineup, and that can make a big difference in any game. Once you do that, everyone else follows."
The Cubs entered Sunday 2-5 without Fowler.
"In 162 games, your depth is normally tested, and ours is being tested right now," Maddon said. "There's nothing to complain about. We scored enough runs [Saturday night in a 9-6 loss], we just didn't pitch like we normally do."
Worth noting
• Jason Heyward has had some tough luck, hitting balls right at defenders. The Cubs outfielder entered Sunday's game 1-for-11 on the road trip and batting .229 overall.
"We're not winning and I'm not helping the team, and that drives me crazy," Heyward said. "Other than that, you get out sometimes, whether it's pretty or ugly."
Timing wise, Heyward feels good.
"That's the way it goes, that's the way the game is," he said. "You do it right, and it doesn't work out."
"He's had a lot of bad luck," Maddon said. "I want him to keep doing what he's doing. He handles it well. There's nothing you can do about it. It's all about geometry sometimes. He's just hitting balls at people well. Just go back and take your next at-bat, and he's done that."
• Adam Warren gave up two runs on three hits and four walks and struck out three over 3 2/3 innings for Iowa on Saturday in a 6-5 loss to Oklahoma City. The right-hander threw 59 pitches, 31 strikes, as he continues to get stretched out for one start with the Cubs prior to the All-Star break. He was expected to make one more Minor League start. Mark Zagunis, Jeimer Candelario and Dan Vogelbach each hit solo home runs for Iowa.
• According to MLB.com's Jonathan Mayo and confirmed by a club source, the Cubs have signed sixth-round Draft pick Chad Hockin to the full pick value of $241,000. Hockin, who is Harmon Killebrew's grandson, flashed closer stuff for Cal State Fullerton. The Cubs also have signed eighth-round selection Stephen Ridings and ninth-round pick Duncan Robinson, who played for Dartmouth.
2016 Draft: Signing and bonus tracker
The Cubs' third-round pick Thomas Hatch started for Oklahoma State on Saturday in the College World Series and took the loss against Arizona. He gave up four runs on five hits and two walks over two-plus innings.
• Former Cubs All-Star Jim Hickman died Saturday at the age of 79. The outfielder, known as "Gentleman Jim," played for the Mets (1962-66), the Dodgers ('67), the Cubs ('68-73) and the Cardinals ('74). He was an All-Star in '70, batting .315 that season with 32 home runs and 115 RBIs.