Martinez hit .167 (5-for-30) in 21 games for the Phillies this season. He hit .300 (73-for-243) in 71 games for Lehigh Valley.
Hernandez appeared in nine games for the Phillies from May 29-June 8, going 7-for-28 (.250). He hit .314 (126-for-401) with 13 doubles, nine triples and 37 RBIs between Double-A Reading and Lehigh Valley.
"[Martinez] is a good kid," Amaro said. "He works hard [and] he's a versatile player. … He hasn't had an extended period of success offensively, but he's a versatile player. He plays the outfield, plays the infield. … There aren't many guys that can play short, play center, and play basically every single position on the field except catcher.
"We're giving [Hernandez] opportunities to play all over the place, because he's got value in his bat and his offense. I think he's good enough to be an everyday second baseman at the big league level, but Chase Utley is our second baseman. So, [the callup] gives him an opportunity to come up here and play up here a little bit."
The two pitchers acquired by the Phillies in the trades for Young and McDonald each have what Amaro calls "big arms," and he looks forward to seeing what they can do in the organization.
Right-handed reliever Nefi Ogando went 2-3 with a 4.09 ERA in 33 appearances (55 innings pitched) for Boston's Class A affiliate in Salem. Left-handed starter Rob Rasmussen went 3-11 with a 4.11 ERA in 28 games (24 starts) between Double-A Chattanooga and Triple-A Albuquerque in the Dodgers' system.
"[Rasmussen] is a smaller lefty with a big arm," Amaro said. "He's starting now. He could be a guy later on that pitches in the bullpen.
"Nefi's the same way. Ogando has a real big arm. He can throw up to 97 [mph]. We'll take a chance on a big arm."
Manny Randhawa is an associate reporter for MLB.com. Follow him on Twitter at @MannyBal9. This story was not subject to the approval of Major League Baseball or its clubs.