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4/28/2013 11:14 A.M. ET

Nelson designated; Arenado set to get his chance

No. 2 ranked prospect will take over for the Rockies as starter at third base

PHOENIX -- The Rockies are ready to turn third base over to touted prospect Nolan Arenado.

The club designated regular third baseman Chris Nelson for assignment after Saturday's 3-2, 10-inning loss to the D-backs at Chase Field. As expected, the Rockies called up Arenado, 22, from Triple-A Colorado Springs for Sunday afternoon's series finale.

The Rockies have 10 days to decide whether to trade Nelson, release him or assign him outright to the Minors. Nelson, 27, went 0-for-3 Saturday and is hitting .242 with no home runs and four RBIs through 21 games. Nelson, the team's top Draft pick in 2004 out of Redan High School in suburban Atlanta, became the starter at third base last season and, despite going on the disabled list twice with a wrist injury and an irregular heartbeat, finished the year with a .301 batting average.

Arenado, a second-round pick in 2009 out of El Toro High School in Lake Forest, Calif., has hit .364 with three home runs and 21 RBIs at Colorado Springs. The Sky Sox were in Tucson, Ariz., Saturday night and did not use Arenado in their 7-3 loss to the Tucson Padres. MLB.com ranked Arenado the Rockies' No. 2 prospect and the No. 66 prospect in the Minors going into this season.

In Spring Training, Arenado started hot and appeared to be making a bid for a Major League job, but he tailed off to a .278 batting average.

The Rockies wanted to make sure Arenado would be ready when called. A big test was the start of this season at Colorado Springs.

Last year as the Rockies sank toward the National League West basement, speculation circulated that they would give Arenado an early callup from Double-A Tulsa. But front office officials weren't sure of his maturity. After he didn't receive the call when the buzz was hot, Arenado's performance dipped. However, Arenado finished the regular season and playoffs as one of Tulsa's leaders.

Although he didn't finish camp as hot as in the beginning, the Rockies were happy with the lean body he displayed upon arriving at camp and the way he handled Spring Training. Arenado hit for power early in the Triple-A schedule, and since then has maintained a strong average, and 11 of his 24 hits have been doubles.

Thomas Harding is a reporter for MLB.com. Read his blog, Hardball in the Rockies, and follow him on Twitter @harding_at_mlb. This story was not subject to the approval of Major League Baseball or its clubs.