Colorado is "aggressively pursuing" the pair of veteran right-handers.
Even with Volstad in the fold, the Rockies are aggressively pursuing free agents Carl Pavano, a right-hander they have tried to acquire numerous times over the last few seasons, and Derek Lowe, a sinkerballer who has pitched well at Coors Field.
The Rockies would like to finalize a deal with another veteran this week.
Pavano, 37, missed most of the 2012 season with a shoulder capsule injury, making just 11 starts for the Minnesota Twins in his fourth and final season with the club. The right-hander amassed an unimpressive 6.00 ERA in his 63 innings on the mound last season, but his ineffectiveness could very well have been a result of his ailing shoulder.
Lowe, 39, is looking for a club that will allow him back in to a rotation after spending the last half of 2012 working out of the bullpen in the Bronx. The veteran right-hander owns an ERA over 5.00 in his last two seasons as a starter, but his high ground-ball tendencies could help his numbers in cavernous Coors Field.