PHOENIX -- Some things, you just don’t plan.

Post-Prince Fielder, Mat Gamel was set to become the Brewers’ first baseman. Then he banged into a wall in San Diego while fielding a foul pop last May 1 and wrecked his knee. Done for the season … and Corey Hart (who moved to first base) and Norichika Aoki (who replaced Hart in right field) emerged as answers.

Late July, the Brewers shipped Zack Greinke to the Angels … and here came starters Mike Fiers, Marco Estrada and Wily Peralta.

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Amazingly, from the point they pulled the plug and dealt Greinke, Milwaukee compiled the fifth-best record in the majors the rest of the season. And from Aug. 20 on, the Brewers tied the Athletics (29-13) for the majors’ best record.

Some things you just don’t plan. Can’t plan.

And that’s where Milwaukee general manager Doug Melvin comes in.

This side of the Giants’ Brian Sabean, with two World Series titles in the past three seasons, no GM in the game has been more nimble and creative than Melvin.

Typically, the 60-year-old GM, entering his 11th season in charge of the Brewers, deflects the praise. In this case, to manager Ron Roenicke and his staff.

“We played well,” Melvin says of last August and September. “Credit goes to Ron and his coaches for not giving up and throwing in the towel.”

Under Melvin, that’s something the Brewers never do.

So here they are, two years post-Prince … and Hart, after establishing himself at first base, likely will miss the season’s first month -- and, likely, more -- following surgery on his right knee Jan. 25.

After banging 30 homers and knocking in 83 runs last summer, Hart thought he could beat the doctors’ projections and sneak back early.

Nope.

It’s looking like the first part of May at the earliest. Realistically, probably mid-to-late May.

Some things you just don’t plan.

“I don’t know,” Hart says. “It’s such a different injury than I’ve had before. I don’t know how fast I can push it.”

And this is a guy who’s pushed the limits. Torn arch in his foot last September. Oblique strain. Appendectomy.

“It’s frustrating,” Hart says. “Honestly, it’s an important year because I’m a free agent at the end of it. I want to make these guys want to keep me.”

Hart’s heart is in Milwaukee, just loves the place, and why not? The Brewers pack Miller Park and they have a chance to win more often than not.

“Things happen, you’ve got to embrace ‘em,” Hart says of last summer’s chain reaction that sidelined Gamel, moved him to first and plopped Aoki in right field.

The Brewers’ marketing department could stamp that as the franchise motto.

They had a great run with CC Sabathia, tried to resign him and survived when they didn’t.

They had a great run with Fielder, and Greinke, and lived to tell about it afterward with last September’s sudden emergence.

Hart transitioned to first on the fly. Before 2012, he had only played two big-league games there, just one start.

But Roenicke plugged him in at first last May 21, and Hart didn’t commit an error in his first 59 games. Brewers infielders loved throwing to a 6-foot-6 target (Fielder is listed at 5-11 but in reality is closer to 5-9). Pitchers -- Yovani Gallardo and Co -- loved Hart’s glove and passion.

“It became fun,” Hart says. “I love digging balls out for guys.”

Without Hart early this season, the Brewers will mix-and-match, as they so often have done. Alex Gonzalez will transition to first from shortstop (Taylor Green and Blake Lalli, the catcher-first baseman who is having a hot spring with the bat, are candidates for time there, too.).

Gonzalez’s move is in no small part because young shortstop Jean Segura, acquired from the Angels in the Greinke deal, is developing rapidly.

“He’s impressive, man,” Hart says. “He had a slow start last year but went crazy in winter ball. He’s very Starling Castro-like. He’s got all the ability in the world.

“I think he’ll hit more home runs than Castro.”

Even with Segura, and Aramis Ramirez at third base, nowhere is the Brewers’ changing of the guard more evident than at first. During Fielder’s six seasons in Milwaukee, he missed a total of just 13 games. Yes, during that span, he was there for an astounding 959 of 972 games.

So it wasn’t just replacing his bat. And with Hart on the shelf as spring moves toward its conclusion, the Brewers are still caulking the gaps left from Fielder’s dependability.

Offensively, Milwaukee didn’t miss a lick last summer. Had its bullpen not been so leaky, the Brewers would have followed their 2011 NL Championship Series appearance with more postseason fun in 2012.

They led going into the ninth inning 83 times last season … and they gave away 11 of those games. Closer John Axford uncharacteristically struggled for two months. Francisco Rodriguez didn’t help.

Enter Melvin, who this year added former Pirates and Braves closer Mike Gonzalez and Burke Badenhop, who was terrific over 66 appearances in the Rays’ bullpen last year.

Best-case scenario is, last year’s strong finish gives the Brewers a head start on this year with players like Segura and Aoki in place, and with strike-throwing starters Estrada (4.93 strikesouts-to-walks ratio) and Fiers (3.75) more experienced.

“There’s enough talent here to compete,” Melvin says.

One thing we know: It would be a mistake to underestimate him. And them.