Twins SS Jorge Polanco placed on 10-day IL with back tightness

Polanco, 28, is out with back tightness that has plagued him since as far back as last October. He underwent an MRI earlier this week, which showed "no significant differences" from the tests done last year, according to Twins manager Rocco Baldelli. 

The former All-Star shortstop hasn't played for the Twins since June 12.

In 58 games for the Twins this season, Polanco is slashing .245/.340/.389, with seven home runs and 33 RBI. He's first on the Twins in RBI, stolen bases (3) and walks (32). 

The Twins recalled Kirilloff from Triple-A affiliate St. Paul to take Polanco's spot on the active roster. The 24-year-old Kirilloff returns to the majors after spending 10 games with the Twins earlier this season. Kirilloff batted .172/.226/.172 with 12 strikeouts in 32 plate appearances. 

Kirilloff was crushing the ball during his most recent minor league stretch; in 35 games, he batted .359/.465/.641 with 10 home runs and 32 RBI. 

The Twins' former top prospect played 59 big-league games last season, batting .251/.299/.423 with eight home runs and 34 RBI.