"We saw some 95s," Melvin said, "and it looks like has a nice delivery."
For Hatcher, the move from the Dodgers presents opportunities for a change of scenery and potentially a more prominent role. Melvin has been in the process of configuring an effective bullpen mix since losing veterans Sean Doolittle and Ryan Madson to a trade to the Nationals last month, and Hatcher comes with experience in multiple roles.
"I know he's pitched in significant roles before and known to kind of be a tough guy," Melvin said. "Likes the tougher situations, he's pitched deep in games. I hear he's a pretty good influence in the clubhouse and has been through the wars and pitched in meaningful innings in meaningful games, and it's good to have a guy like that."
Hatcher was on the Dodgers' Opening Day roster, posting a 4.66 ERA in 26 appearances before landing on the DL June 23 with thoracic inflammation. The 32-year-old began a Minor League rehab assignment July 29, pitching to a 1.50 ERA in five games, his last coming a week ago.
In three seasons with Los Angeles, Hatcher compiled a 4.64 ERA in 112 games, racking up 131 strikeouts in 116 1/3 innings.
"I've closed some games in the big leagues, I've been the first guy out of the 'pen, I've come in in the third inning," Hatcher said. "I've been the jack-of-all-trades and the master of none, so when they call my name I'll be ready.
"[The Dodgers have] a lot of guys, and I didn't really pitch up to par, and they've got guys throwing the ball well. So it's probably a better move career-wise to get some innings and hopefully I can accomplish that over here and throw the ball well."
The A's optioned right-hander Josh Smith to Triple-A Nashville to make room for Hatcher on Wednesday. They also dealt for lefty Sam Moll from the Rockies for a player to be named or cash, designating right-hander Zach Neal for assignment.
Moll, who was assigned to Nashville, was 3-2 with a 4.18 ERA in 44 relief outings for Triple-A Albuquerque.
Jane Lee has covered the A's for MLB.com since 2010.