Minor Moves: Armstrong, Vitek, Keck, Arroyo, Broxton

We'll keep track of the day's minor moves here:

• Jack Armstrong, a 2011 third-round choice of the Astros, has hung up his spikes, reports Evan Drellich of the Houston Chronicle (Twitter links). Selected as a pitcher and given a $750K signing bonus, Armstrong never even got on the hill professionally due to a series of arm injuries. He had been hoping to switch to first base. 
• 2010 Red Sox first-rounder Kolbrin Vitek has retired, reports Alex Speier of WEEI.com. Injuries slowed the toolsy player, who never managed to translate his raw abilities into production. As Speier notes, however, several other players taken in that draft have panned out quite nicely.
• Reliever Jon Keck has signed on with the Rockies on a minor league pact, according to the MLB transactions page. The 25-year-old southpaw had spent his entire career in the Royals organization, and threw 52 relief innings of 3.81 ERA ball at the Double-A level last year. It would appear that he had some significant control issues, however, as he walked 6.8 batters (striking out 8.7) for every nine innings.
• The Diamondbacks have acquired lefty Spencer Arroyo from the White Sox for cash, according to the MLB transactions page. The 25-year-old spent most of his time as a starter in Double-A last year, putting up a 3.50 ERA in 149 1/3 innings while posting 5.8 K/9 against 2.7 BB/9. 
• The Pirates have acquired outfielder Keon Broxton from the Diamondbacks in exchange for a player to be named later, Pittsburgh announced via press release. Selected 95th overall in the 2009 draft, Broxton was outrighted off of the Arizona 40-man roster back in October. Broxton has struggled to translate his athleticism — he was the D'backs most athletic prospect last year, per Baseball America — into consistent production. Playing at Double-A last year, Broxton was unable to follow up on a strong 2012 campaign in his repeat of the HIgh-A level, and hit just .231/.296/.359 with eight home runs and five steals in 372 plate appearances.
• At the start of the day, two players — Carlos Peguero of the Royals and Johnny Monell of the Orioles — were in limbo in the MLBTR DFA Tracker. They have since been joined by Bobby LaFromboise of the Mariners and Raul Valdes of the Astros.