PHOENIX – It has been easy to overlook the season of Kevin Youkilis.

Amidst the arrival of Adrian Gonzalez, the resurgence of David Ortiz and Josh Beckett and the emergence of Jacoby Ellsbury, Youkilis has been the sometimes-obscure presence in the middle of the Red Sox lineup. Even among Sox players returning from injury, Youkilis’ status this year has garnered far less attention than that of teammate Dustin Pedroia.

It seems almost oxymoronic to suggest that a player can be unnoticed as an All-Star, yet that is precisely what Youkilis has been in 2011. He slipped in and out of his third All-Star Game with little fanfare (collecting a hit in his only at-bat) as manager Ron Washington’s choice to replace Alex Rodriguez when the Yankees third baseman proved unable to play due to his knee injury.

Yet his level of play, particularly after his injury-truncated season, has once again been elite. After his 2010 season – in which he was posting career-best numbers – was cut short by surgery to repair a torn adductor muscle, Youkilis has crossed the diamond from first base to emerge as one of the top offensive third basemen in the game.

He is hitting .285 with a .399 OBP, .512 slugging mark and .911 OPS to go with his 13 homers and 63 RBI. His OBP, slugging percentage and OPS are all tops among major league third basemen. He ranks among AL leaders in extra-base hits (40; 9th), OPS (7th) and RBIs (6th), and he’s on pace for 23 homers and 113 RBI.

Youkilis is not and has never been terribly concerned with such numbers, however. He has always defined himself more through the relentlessness of his effort.

While players are often taught to measure their effort levels to withstand the rigors of the seemingly endless 162-game schedule, Youkilis (who has played 83 first-half games despite a host of nagging injuries, and is on pace for a career-high 149 games) is a believer in red-lining.

“You can always expect me to play the game as hard as possible. I’m going to do everything in my capability to play as hard as I can and leave it out on the table,” said Youkilis. “That’s how I play the game. I’ll run every groundball out and play till the final pitch is done.”

The motivation, Youkilis suggests, is internal. There is a constant sense of restlessness regarding his achievements.

On the one hand, he still expresses amazement whenever he is placed in the environment of an All-Star Game. On the other, even though his status as a three-time All-Star since 2008 has cemented his place among the top players in the game in recent years, he has not become complacent about his position.

“I’m never really satisfied with what I do any year,” Youkilis said. “I always think I can do better.”

That belief, and the consequent approach that it yields, comes with consequences. Over the course of a season, Youkilis appears almost masochistic as he embraces an injury-prone style of play.

Talent evaluators admire the player’s intensity, even as there is an understanding that it results in times when he is hurt. The physical punishment – given his setup in the batter’s box, he is constantly either getting hit by pitches or slamming foul balls off of himself; in the field, he throws himself after groundballs with abandon – is apparent.

Youkilis’ inability to relax his energy level even for a pitch has likely put a clock on his career. There is only so much punishment that an athlete’s body is intended to take. Youkilis regularly tests that limit.

Yet even if his style of play comes at the expense of career longevity, Youkilis has no intention of compromising that approach.

“I could end my career this year knowing that I’d played as hard as I could, and I’d be satisfied with that,” said Youkilis. “I’m not worried about years in the game. I’m just worried about playing the game as hard as I can as long as I’m here.

“I don’t think I’m going to be playing the game until I’m 40 years old. I think I can say that now. I’d rather play as hard as I can, and when it’s my time and I’m personally ready with no outside influences to end my career, it will be over.”

That said, he isn’t exactly getting ready to call a press conference to announce his retirement. He is now 32 years old and in the third season of a four-year, $41.125 million deal he signed prior to the 2009 season. The contract includes a team option for the 2013 season, when Youkilis will be 35.

Youkilis said that he will “definitely play for another [deal] … [for] a few more years after” the end of his current deal. He noted that he would reach 10 big league seasons in the middle of the 2014 season, something that would assure him of a full pension whenever he does walk away from the game.

“Gotta have that pension down the road,” he smiled. “Gotta go on those fun trips when you’re in your 60s, enjoy life. Make up for all the times you don’t get to go on vacations now.”

For now, however, he looks like someone who is consumed by his work. Given his style of play and the toll it takes on him, it has become intriguing to contemplate whether Youkilis might end up transitioning in coming years to a hybrid third base and DH role.

With David Ortiz’ contract up at the end of 2011, if the Red Sox do not re-sign him, there will be few viable options by which to replace Ortiz’ production at a position whose sole value is measured by offense.

Should Ortiz not be brought back, one possibility would be to give Youkilis – who, for the first time in his career, has served as a DH in a smattering of four games this year (“It’s helped out with some of the bumps and bruises,” he notes) – more time at DH to spare some of the punishment that he typically absorbs.

It is a prospect that Youkilis treats without great enthusiasm. He feels that it is more difficult to remain physically and mentally engaged in the game without being in the field. That said, he is certainly willing to consider it if approached by the club.

“I wouldn’t want to DH until I had to DH. I like playing the field. I like being involved in the games,” said Youkilis. “[But] it wouldn’t be the first time that the Red Sox asked me to do something different, or whatever team I’m playing for. I’ve always been just a team player. If that’s the role that I have to play to help the team win, I’ll do it.”

Youkilis noted his appreciation for the fact that GM Theo Epstein and manager Terry Francona have made a point of sitting down to discuss the team’s plans for him at the end of each season. While his ability to shuffle between first and third has been a significant boon to the Sox at times, the movement can be unsettling.

Yet because of how the Sox have engaged him in dialogue about his positional shifts, Youkilis has felt that the transitions have been manageable. And he appreciates the likelihood that, if the Sox ever do want to employ him as a DH, they will do so not by fiat but instead with his feedback.

“That’s the great thing about Boston. Theo and Tito are always great with me talking about, the next season, what’s going to happen,” said Youkiils. “I’d give them my honest opinion. It wouldn’t just be like, ‘Oh, yeah – just put me out there.’ If I felt like I wanted to play the field, I would be honest with them. But also, I want to stay in Boston and if that were the only way I’d stay in Boston, that would be one of the [talking points], too.”

Yet those are all more distant concerns about what lies ahead for Youkilis. For now, for both the player and the Sox, such considerations gloss over what he has been this year.

In a year when Gonzalez and Ortiz have been among the top sluggers in the game, Youkilis has quietly been the right-handed counterbalance in the cleanup spot. With little fanfare, he has once again performed at a level that places him in select company, something that seems somehow fitting to a player who has quietly carved out a career as a blue-collar star.