In return for Hellickson, the Diamondbacks received Rookie-level right-hander Sam McWilliams, as John Gambadoro of Arizona Sports 98.7 reported.
The Phillies are taking a calculated risk by acquiring Hellickson.
A former Rookie of the Year, Hellickson at the least will be able to fill innings in Philadelphia, where their rotation is void of back-end starting pitching.
However, Hellickson serves a double-purpose. If he can re-find some of his old magic, Philadelphia may be able to trade him at either the 2016 or 2017 trade deadline and get more prospects in return than they gave up to get him.
For Arizona, Hellickson was likely to get a raise in arbitration this offseason and the team was thought not to want to tender him a contract. It appears that they attempted to get whatever they could for him, as by dealing him they are at least able to get some prospect return, as opposed to non-tendering, or releasing, him.
The 28-year-old Hellickson had an average season in 2015.
He went 9-12 with a 4.62 ERA (4.44 FIP; 4.16 xFIP) in 27 starts and 146 innings this season, missing some time due to hamstring issues. He posted a 2.81 strikeout-to-walk ratio, striking out 121 and walking 43, the best mark of his career (min. 50 IP).
Hellickson's best season was his rookie year when he was with the Rays. He went 13-10 with a 2.95 ERA in 29 starts, en route to the Rookie of the Year award.
The Diamondbacks received a low-level prospect in return.
McWilliams, 20, has not advanced past Rookie-level ball since being drafted in 2014. He was rated as the Phillies No. 27 prospect in their Top 30, according to MLB Pipeline.