Cain and second baseman Chris Getz were returned from their Minor League rehabilitation assignments with Triple-A Omaha and pitcher Nate Adcock and infielder Irving Falu were optioned to Omaha, the Royals announced on Monday.
The Royals will resume their schedule on Friday night against the White Sox at Kauffman Stadium.
Named the starting center fielder in Spring Training, Cain never made it to Kansas City, at least on the field. After playing in the opening series at Anaheim, he was injured while running into the center-field fence making a catch at Oakland in the season's fifth game. He's been on the disabled list ever since, first with a left groin strain and then with a torn hip flexor, also in the left leg.
Cain went just 2-for-15 (.133) with one RBI before being injured. Obtained from Milwaukee in the Zack Greinke trade, he spent the 2011 season with Omaha and showed enough with a .312 average, 16 homers and 81 RBIs that the Royals felt confident he could play in Kansas City. Therefore, they were comfortable in trading center fielder Melky Cabrera, who was a year away from free agency.
Called up in late September last year, Cain was 6-for-22 (.273) in his first six games and displayed great speed and range in the outfield.
Getz, out since June 18 with a lateral strain in his lower left leg, was on his second stint on the disabled list. Earlier in the season, he had a left rib cage contusion and missed three weeks. So, he's appeared in just 36 games, batting .290 (29-for-100).
Meanwhile, Yuniesky Betancourt has taken over the second-base job, becoming a productive hitter and playing well, defensively.
Adcock was on his fifth stay this season in an up-and-down odyssey between Kansas City and Omaha. He's 0-3 with a 2.67 ERA in 10 games including two starts with the Royals.
Falu, a utility infielder in his second stay in Kansas City, hit .321 in 15 games with five RBIs. With the departure of outfielder Mitch Maier, Falu has the distinction of being the longest-tenured Royal, drafted in 2003.
Dick Kaegel is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.