SCOTTSDALE, Ariz. >> Buster Posey squatted into a catcher’s crouch for his first spring training bullpen session and began receiving pitches from ace Tim Lincecum, then Matt Cain.

He practiced springing up to throw after catching the ball, with no hesitation or signs that he had ever been seriously hurt.

Posey showed he has plenty of pop in his bat, too. He cleared the fences a couple of times in his first round of batting practice at Scottsdale Stadium on Sunday, Day 1 for Giants pitchers and catchers.

After bench coach Ron Wotus surrendered those home run balls, Posey quipped: “Four-seamer coming at 55 (mph), I tend to square that one up.”

Clearly, San Francisco’s cleanup hitter is loose, good-natured and in a positive frame of mind.

“It was special for me because I’ve put in a lot of work to get back to this point and this is just another step,” Posey said. “There’s still some work to do but I was very happy with today.” 

More than 50 fans lined the fences throughout the ballpark trying to catch a glimpse of Posey getting back to work with the team at last.

“For him, it’s an important day,” reliever Santiago Casilla said. “He’s waited a long time to play. He’ll be OK. He’s been working hard. Everybody wants to watch him.”

The 2010 NL Rookie of the Year made his highly anticipated return to the field in a formal setting after a season-ending leg injury last year. He tore three ligaments in his left ankle and broke a bone in his lower leg in a frightening home-plate collision with Florida’s Scott Cousins on May 25.

Posey is one of a handful of key major leaguers working back from injuries this spring  —  including Cardinals pitcher Adam Wainwright, Colorado’s Jorge de la Rosa and reliever Joba Chamberlain of the Yankees. 

Through his entire ordeal, Posey has been able to reflect on his baseball career.

Yes, he wants to keep catching for years to come, though changing positions did cross his mind a few times. He refuses to get involved in speaking out about the need for any rules changes when it comes to making contact with the catcher (manager Bruce Bochy is handling that campaign). Posey wants to do everything he can to stay in the lineup as a regular.

“I think it’s just a greater appreciation for doing what I do, just enjoying this, being out here today catching a couple of pens and maybe some of the not-so-glamorous stuff of a catcher’s job,” he said. “Enjoying that stuff a little bit more and just knowing that it can be gone quick.” 

General manager Brian Sabean, Bochy and the brass kept a watchful eye on Posey in the bullpen. It was a monumental moment for Posey, whose long road to recovery included having screws removed from his surgically repaired left ankle in July and pushing himself around on a makeshift scooter to keep weight off the injured leg. 

Everybody is encouraged seeing Posey in uniform.

“I threw to him Friday,” left-hander Madison Bumgarner said. “He looked normal to me, ready to go, like he hadn’t missed a beat.”

The Giants have a plan in place to keep Posey from overdoing it now — and he understands that. He will do all he can to avoid another injury that could derail his plan and force him to become a full-time first baseman.

It would mean a lot to Posey to play in the first Cactus League game March 3 against defending NL West champion Arizona, and Bochy believes that’s possible. For a while, Bochy will check in with the medical staff after each of Posey’s games in which he catches five or six innings.

Posey won’t catch bullpens Monday but is expected to participate in other baseball activities.

“That’s our decision, not his,” Bochy said.

Sabean watched Posey during the fall as he began catching again.

“He thinks everything is fine,” Sabean said. “He’s ready to get out here. It’ll be us holding him back.”

These days, Posey said he consciously thinks about picking up his 6-month-old twins — daughter Addison and son Lee — by squatting down first as to not aggravate anything. It’s all of these little things he has learned through what became a painful blow to the Giants, who missed the playoffs a year after winning the World Series.

After Lincecum’s session, the right-hander greeted his catcher with a friendly handshake and thumbs-up. 

“It just kind of picked up where we left off,” Lincecum said. “It’s nice having a chance to do that down here and just kind of having a clean slate and a new season to work with. He’s got a new season to work with. I don’t think he’s thinking about the injury too much.”

Posey has distanced himself from the collision — though he has watched it multiple times — and the emotional aftermath. Cousins has expressed how sorry he is the injury happened but called it an aggressive baseball play.

Posey said Sunday he accepts that Cousins does care, even if they haven’t spoken despite efforts by the Marlins outfielder.

“The biggest thing for me back then and now is looking forward and being positive and trying to get ready for another season,” Posey said.

Posey has regained his rhythm at the plate in a hurry. Even when he first started hitting last fall after about five months off, the swing came back fairly quickly.

“I’m blessed in a sense. I enjoy this game,” he said.

Posey’s presence was missed every day last year. 

In 2010, he wasn’t even called up from Triple-A Fresno until late May but still batted .305 with 18 home runs and 67 RBIs in 108 games to help the Giants capture their first NL West crown since 2003.

This is the player San Francisco gave $6.2 million when he signed in August 2008 as the fifth overall pick out of Florida State, the richest deal ever for a Giants amateur.

“I know they’re glad to have him back,” Bochy said. “He’s very popular in the clubhouse and they know how long a road he had to endure in his rehab. That’s a tough road. The talent he brings makes us a better club.”

Not to mention all the other intangibles.

“Buster’s the core of this team just because he’s on both sides, offense and defense. He’s our leader,” left-hander Barry Zito said. “It’s good for the morale of the team. We feel like we’re a full unit again.”