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2/25/2014 7:21 P.M. ET

Rodriguez thrilled with first live session since TJ surgery

PHOENIX -- Fernando Rodriguez bettered himself as a pitcher even when he couldn't throw, intently studying peers from the dugout during a lengthy Tommy John rehab program last year.

On Tuesday, the A's right-hander brought his findings to the mound, to face hitters for the first time since the surgery last March, and he surprised even himself.

"Not what I expected it to be, I guess, because I had such an adrenaline rush, so the ball was flying out of my hand," Rodriguez said. "It's kind of exciting. It's something I've been waiting for a while. I couldn't have asked for a better day for it being the first time throwing off the mound to hitters."

Rodriguez threw 20 pitches, utilizing mostly his fastball and a few changeups, and impressing with tweaked mechanics that allow him to get the ball to the plate quicker.

"It's a good feeling for you when you work that hard," said manager Bob Melvin. "All the changes he looks to make from last year, he incorporated into throwing to hitters today. He was down in the zone with his fastball from a high angle, had a good changeup and, really, all the hard work has paid off to this portion so far. Credit him for all the hard work, because he has a chance to be a nice piece for us this year."

Melvin is still iffy about getting Rodriguez into a Cactus League game but has said the righty will at least see simulated game action by spring's end. The plan is for Rodriguez to remain in Arizona for extended Spring Training, before he'd even be considered to join the big league team, which is already packed with experienced relievers.

The 29-year-old has yet to throw a pitch for the A's following a trade from Houston with Jed Lowrie last February. But he's stayed busy in the meantime.

"I talked to Chili [Davis] a lot last year, and also with Bartolo [Colon]," he said. "The biggest thing Bartolo told me was, 'I've seen a lot of guys come back from the surgery. What you have to do is just work on your location and let the velocity come later.' So that's what I wanted to do this offseason, work on the little things.

"Today, I was able to actually see it. This is huge. I was very happy. Even now, I'm almost flying a little bit. After a whole year of not being able to compete, this was a big step."

A's will have 10-game test run on new replay rules

PHOENIX -- Bob Melvin attended a two-hour meeting with fellow Cactus League managers on Monday to be further educated on the new instant-replay rules. He came out of it feeling "dizzy."

"It was a long meeting, and rightly so," the A's manager said. "There were certainly a lot of things I hadn't thought of before. There are just a lot of things you could potentially review, and I think they did a great job of designating what's reviewable and what's not and why, and it made a lot of sense."

The rules will be implemented for real during the season, but Melvin will first have the opportunity to test out the new system this spring during all televised games. For the A's, that's 10 games in which Melvin will be encouraged to challenge plays and explore the process.

He's thankful for the learning curve.

"I got the answers for the most part," he said. "I think Spring Training will be a part of that process, and hopefully we get some of the kinks worked out before we get to the start of the season."

Prior to this season, replay had been utilized only on home runs, to review whether they were fair or foul, in or out of the ballpark. Now, it will be available for almost all plays that don't involve a strike-zone call.

Managers receive one challenge during the first six innings of each game, though if they successfully get a call overturned, they receive another. Once the seventh inning begins, replays will be at the discretion of the umpires.

Rules governing plate collisions were also released Monday, and Melvin was pleased to find they don't read much differently than before, noting that they're simply "more succinct with the language."

The experimental regulation states that catchers can only block the plate if they have possession of the ball, while runners are not allowed to deviate from their direct path to the plate to initiate contact with the catcher. Moreover, runners are not allowed to lower their shoulders or push through with their hands, elbows or arms when veering toward the catcher.

Runners who slide, and catchers who provide them with a lane to reach the plate, will not be found in violation of the rules.

"I think they addressed what issues they thought were most important and most prevalent and kind of went with that," Melvin said. "See how it goes and take further steps maybe down the road. It's that one where the ball takes you into the line, where it's going to be a bang-bang play, that will be the most difficult."

This play is among those deemed reviewable by video replay.

Worth noting

• Manager Bob Melvin is already regretting his recent decision to create a Twitter account, so much so that it's been deleted.

"I haven't changed it. I just blew it up," he said, smiling.

Though Melvin never revealed his Twitter handle to the media, more than 100 fans were able to identify and follow him on the social-media site. For every new follower, an overwhelmed Melvin received an e-mail.

"It was an uncomfortable day," he said. "Notifications and all that, wow."

Jane Lee is a reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.