In 31 games with the Sox, Middlebrooks has a .302/.345/.531 line, with six homers and 22 RBIs. He hit the ground running and hasn't looked back.
"It's flown by, to be honest," Middlebrooks said. "It's been more than I expected. The first couple days went by quick, everything was moving fast. But it's a daily thing, parts of a game can speed up on you, that's part of the game. The good ones here are able to slow the game down, and that's what I'm learning to do."
Middlebrooks made his big league debut on May 2 when he was recalled from Triple-A Pawtucket. The Sox needed him to fill in for the injured Kevin Youkilis.
No big deal for a 23-year-old rookie, right?
All Middlebrooks did was reach base safely in his first three plate appearances, drive in nine runs in his first four games and begin his career with a five-game hitting streak. That stretch included his two-homer, five-RBI outburst on May 7 vs. the Royals.
With extra-base hits in each of his first five games, Middlebrooks became the first player since 1900 to open a career in that fashion. The other? Enos Slaughter in 1938 with the Cardinals.
Middlebrooks knew he could compete in the Majors, and the early results reinforced his confidence.
"Once I was up here for the first couple of weeks, I really went, 'OK. I can play here,'" he said.
The accolades don't stop there. Middlebrooks is the first Red Sox player with 35 hits and 22 RBIs in his first 30 games since Fred Lynn in 1974-75. And those nine RBIs in his first four games matched the Major League record, according to the Elias Sports Bureau.
"It's awesome, just really cool," said Ryan Kalish, who played with Middlebrooks in Pawtucket. "Will is doing what everyone really expects him to do."
And it's not as if Middlebrooks started hot and cooled once pitching staffs adjusted to him. He's hit safely in 23 of 31 games, including 30 starts.
"He's got power and a really good approach at the plate," said catcher Jarrod Saltalamacchia. "It's not like he's a dead-red fastball hitter, he's been hitting a lot of offspeed pitches well and driving the ball to both sides of the park. He plays a good third base, too."
The way his manager raves about him, one might think Middlebrooks is more veteran than neophyte.
"I think he has a real professional approach to the game," Valentine said. "I like his work ethic, I like his swing, I like his fielding, I like his game awareness. He's confident. He understands what the competition is all about."
Middlebrooks, though, doesn't focus on the comparisons, the records or the praise.
"Being able to come up here and help win games is my main thing," he said. "That's what I wanted to do -- come up and gain their trust, let them know I'm here to help and do whatever I can."
Middlebrooks has done that, and more.
"Absolutely," Valentine said. "He's hit over .300, he's hit against some tough pitching, he's driven in runs, he's hit balls really hard. He's been a real good player on our team."
Ask the Red Sox's players or the various Minor League instructors Middlebrooks played for during his rise to the Majors, and one word continually comes up: confidence.
But Middlebrooks is not cocky or brash. No, it's a quiet confidence. It helped him reach the Majors and it's helping him stay there.
"He's a pretty confident player," said Arnie Beyeler, who managed Middlebrooks in Triple-A. "He's just got a lot [of] ability, but when he's got the confidence going, seeing the ball well, it kind of shows that, 'Hey, I can play up here, I belong up here.' And that helps. I'm sure he's fed off that."
Said Saltalamacchia: "I definitely see a confidence to where he knows he belongs. He's playing with that confidence, and that's why he's doing so well."
When did that fortitude begin?
"It started in high school, really," Middlebrooks said. "I've been around sports my whole life, my dad's been a coach for a while, so I just know how important confidence is. And when you have it, you just kind of have that edge."
Of course, talent is generally a precursor to confidence. And Middlebrooks isn't lacking in that department.
At Liberty-Eylau High School in Texarkana, Texas, he was a star on the basketball court and a standout quarterback of the state championship football team.
The Red Sox made him their fifth-round pick in the 2007 First-Year Player Draft. Instead of attending Texas A&M University to play baseball and football, Middlebrooks signed with the Sox.
Middlebrooks quickly rose through the Red Sox's farm system. Over three levels in the Minors last season, he combined to hit .285 with 23 homers and 94 RBIs. This year, he hit .333 with nine homers and 27 RBIs in 24 games with Pawtucket prior to his promotion.
It wasn't always easy.
Middlebrooks struggled at times in Class A ball during his first three seasons in the Minors. Middlebrooks knew he would make it to the Majors one day, but he had to learn how to be a professional first.
"The first couple years of pro ball, it was tough because I was failing and I had never done that before," he said. "I really had to learn how to dig myself out of holes and not ride that emotional roller coaster. But really, probably last year was when I started realizing I was getting close and if I could just stay consistent, maybe I could get there."
Jonathan Hee came up through the Red Sox's farm system with Middlebrooks. Before the two even got to Triple-A, Hee knew his teammate would be in the big leagues sooner rather than later.
"I knew the first time I met him," Hee said. "The first day I saw him, he was such a good athlete -- big, good frame, pure athlete. He doesn't let a lot of things go to his head, which is really special. He's an unbelievable player, and it's showing right now."
Middlebrooks credits much of his success to his father, Tom, his childhood baseball and football coach.
"He was the one who was always going to the field with me, throwing with me in the yard," Middlebrooks said. "That was my go-to guy when I was growing up."
Nowadays, the father-son dynamic has changed.
"At this point, he's like asking stuff from me now, we kind of flipped the script, so it's cool. He's there for me, really positive, tells me every day, 'Go have fun playing the game you love,'" Middlebrooks said.
Living out his dreams as the starting third baseman for the Boston Red Sox at age 22, Middlebrooks is pleased with how far he's come from a remote town in East Texas.
"Absolutely, but at the same time, I'm not satisfied," he said. "I want to stay here for a while. I want to stick and win a World Series."
Yes, this is only the beginning.