Volstad was placed on waivers in order to clear a roster space for Roy Oswalt. The 26-year-old allowed 10 runs in 8 1/3 innings this season. He posted a 4.79 ERA with 3.3 K/9 and 3.1 BB/9 in 47 innings at Triple-A so far this season.
The 30-year-old Kensing pitched just two-thirds of an inning for the Rockies this season -- his first big league action since 2009. The former second-round pick has a 5.79 ERA in 161 2/3 career innings with 8.0 K/9 and 5.0 BB/9. He's fared significantly better in Triple-A, though, where he owns a career 3.67 ERA with 9.2 K/9 and 3.9 BB/9.