Manager Bud Black said that Castellani will be called up from Triple-A Albuquerque to start the second game of Tuesday's doubleheader with the Giants, Jenny Cavnar of AT&T SportsNet Rocky Mountain reports.

German Marquez is thus in line to start the first game of the day after he had his scheduled start Monday postponed due to inclement weather in Colorado. Castellani will likely be designated as the Rockies' 27th man for the twin bill, so he'll presumably head back to Albuquerque following the spot start. The 25-year-old right-hander made 10 appearances (nine starts) for Colorado as a rookie in 2020, posting a 5.82 ERA, 1.45 WHIP and 25:26 K:BB in 43.1 innings.

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