The moves were largely necessitated by Moscot's injury Monday night. The right-hander separated his left shoulder in the first inning, forcing the Reds to rely on relievers Pedro Villarreal, Nate Adcock and Burke Badenhop for the remaining 7 1/3 innings.
The Reds simply needed to replenish their pitching depth.
"We're just a little beat up," manager Bryan Price said.
Price said Tuesday that the club will know the extent of Moscot's injury within the next 48 hours. Depending on the amount of damage to his shoulder, the rookie's season could be over.
"The significance of the damage will dictate what needs to happen," Price said. "If he can comfortably recover with his arm immobilized for a while in a sling and can heal, then great. If there's extensive damage in the shoulder that would require surgery, that would definitely limit the probability of him being able to come back and pitch this year."
The Reds have not decided who will start in place of Moscot on Saturday against the Marlins.
Cincinnati replenished its bullpen with Contreras and Hand, righties who both have Major League experience.
Hand hasn't pitched in the big leagues since 2013, when he recorded a 3.69 ERA in 31 outings (seven starts) with the Brewers. The 29-year-old has been a member of Louisville's rotation for part of this season and has a 4.50 ERA with a 1.182 WHIP over 44 innings.
"We felt he was best suited to come on out and give that middle relief that we so badly need right now," Price said.
Contreras has appeared in 20 career games -- three this year -- and has compiled a 5.96 ERA over that span (2.70 this season). He had a 4.66 ERA at Louisville.
Boesch had just 59 plate appearances this year and was batting .125 with 21 strikeouts, three walks and only one extra-base hit.
Reds Minor Leaguer Isaac Moncion has been suspended 72 games without pay for violating the Minor League Drug Prevention and Treatment Program, it was announced on Tuesday evening. The 19-year-old right-hander had a 6.48 ERA with the Dominican Summer League Reds. He tested positive for Stanozolol, an anabolic steroid, and his suspension will begin immediately.