Donnie Gardiner doesn’t like to waste time. Not with the Red Sox home opener fast approaching.

After offering a quick greeting at Gate D — “C’mon in. Welcome to Fenway Park,” he says — he rushes off to the visitors’ clubhouse. Gardiner walks and talks.

“We have city inspections we have to worry about,” he says. “We have construction we have to finish up. We have just all kinds of things going on right now.”

When you step into the visitors’ clubhouse, you see and hear what he means. Workers are installing walls, putting ceilings back together, painting, sanding, sawing and hammering. And Gardiner oversees all the action.

The toughest job at Fenway — and, arguably, in all of Major League Baseball — might belong to Gardiner. He’s Fenway's facilities superintendent. That means he makes sure the oldest pro ballpark stays standing and keeps running smoothly.

A lot of critical work takes place well before every home opener. That’s obvious when you watch Gardiner get Fenway ready for Tuesday’s home opener between the Red Sox and Toronto Blue Jays.

Gardiner discusses construction work in the visiting team's clubhouse with a contractor. (Jesse Costa/WBUR)

Inside the visitors’ clubhouse, Gardiner moves from the new whirlpool room to the new training room to the new video coaching room. He gets progress reports and gives advice.

There's talk about changing filters and smoothing out walls and cutting lines. The same thing happens when Gardiner visits the Red Sox clubhouse area and checks on manager Alex Cora’s new, larger office and other upgrades.

Teams have outgrown Fenway’s cozy clubhouses. So there’s always plenty of work to do for the Red Sox and visiting teams.

“I'm not playing one side over the other,” says Gardiner. “Whatever we do for one, we do for the other.”

As for Gardiner’s office, it’s underneath the third base concourse. He proudly mentions that his door does not say, “Facility Superintendent.” Instead, there are signs out front that read: “Dr. Donnie’s Department of Infant Psychology” and “Day Care Provider.”

“I’m an adult babysitter,” he says. “I have a weird sense of humor. And the company lets me be me.”

Gardiner’s quirky sense of humor matches the quirky ballpark he maintains.

He’s 5-foot-3, and a soft-spoken but commanding presence. It’s clear he knows how to handle the unpredictable challenges that come with renovating a 107-year-old ballpark.

He should. He’s worked there for three decades.

“Everything we’ve done to this place has not taken away from the allure of the park,” says Gardiner. “The feel is still there. This building has a feel to it. It does for me personally. I’ve touched every inch of this place at one time or another.”

And with a footprint as small as Fenway’s, every inch matters.

Gardiner likes to say he plays a “Game of Inches.” He’s constantly figuring out how to make the best use of limited space, especially in the clubhouse areas.

Sometimes he’s also working around brass waterlines that have stood the test of time. During offseason renovations, sometimes he’s uncovering remnants from Fenway’s past.

“When we ripped up the concourse a few years ago it was like an archaeological dig, finding the old nip bottles, old shoes," he says. "And the place was, I'm assuming, heated by coal because we found a lot of coal ash out in centerfield.”

When the ballpark reopens for business each season, Gardiner’s focus shifts from renovations to preventative maintenance.

“Game days are actually easier for the most part,” he says. “If we do our job right, the building runs itself.”

But before the games begin again, there’s a lot to do: turn on the water to concession stands, test generators, check emergency lighting, finish the construction in both clubhouses. The punch list goes on and on. And Gardiner’s busy staying on top of it all.

“It’s unlike any other building,” he says. “It’s not Joe’s Pizza. It’s not a high rise. It’s not a supermarket. It’s a very unique building. And the way it’s used is very unique. That’s what I love about it. I’d get bored anywhere else.”

Even if that means putting in 100-hour weeks and, occasionally, sleeping in his office.

One thing Donnie Gardiner doesn’t do: Watch the Red Sox play. He’s too busy monitoring what’s happening off the field.