ANAHEIM—A good trade can define a franchise, just as a bad trade can cripple one.

As the A’s prepare to enter the postseason for the first time in four years, they can look at Khris Davis to see the walking embodiment of one of those franchise-altering trades.

Davis hit his major league-leading 48th home run Saturday night in the Athletics’ 5-2 win over the Angels. The 30-year-old slugger now has 133 home runs over the last three seasons, the most in the majors in that time.

Those three seasons have come after the A’s acquired Davis in a preseason trade with the Brewers in Feb. 2016. The cost to acquire the future major league home run king? A pair of prospects named Bubba Derby and Jacob Nottingham.

“Gotta be one of the better trades ever at this point,” Athletics manager Bob Melvin said. “We felt good about him coming in, and if you look at his first month of his first year it was a struggle for him, and since then it’s been as good a numbers as anyone has put up in the game.”

Nottingham and Derby remain fine prospects in their own right. Nottingham made his major league debut this year and has promise as a 23-year-old offensive catcher. Derby logged a respectable 4.49 ERA pitching in altitude at Triple-A Colorado Springs.

But that can’t compare to Davis. Last year he became the first Oakland A’s player to ever hit 40 home runs in back-to-back seasons, an illustrious title considering the club’s history includes Reggie Jackson, Mark McGwire, Jose Canseco and Jason Giambi, among others. Now he’s done it three years in a row, becoming the first A’s player with three consecutive 40-home run seasons since Jimmie Foxx in 1932-34, when the franchise was still in Philadelphia.

Davis showed hints of big power in Milwaukee. He hit 60 homers in two and a half seasons there. But when he got to Oakland, things went up a notch.

“I thought I could hit 40 before I did,” Davis said. “It was just a matter of time before it showed up, but I was patient and it did when I got here.”

Being undervalued and flourishing later fits the theme of Davis’ career.

Davis was a part-time player his first two seasons at Cal State Fullerton and hit only four home runs combined those two years. He finally got everyday playing time as a junior in 2009 and took advantage, leading the Big West Conference in doubles (25), home runs (16) and total bases (149).

Despite his big numbers, he still fell to the seventh round of the 2009 draft—where he was picked between a pair of righthanders named Sean Black and Brady Colvin—largely because of his 5-foot-10 frame.

But Davis always got to his power. He set low Class A Wisconsin’s franchise record with 22 home runs in his first full season and ultimately hit 69 homers in just over three seasons worth of games in the minors.

He hit 11 homers in his first 56-game stint with Milwaukee in 2013 and has successively increased his home run each season from there, culminating at his ascent to the major league lead.

“He has the ability to do stuff that some guys just don’t have,” said A’s utilityman Mark Canha, a teammate of Davis’ all three seasons. “He’s so strong and flexible in so many ways, it’s hard to achieve the positions he gets himself into.”

Trading Davis certainly hasn’t torpedoed the fortunes of the Brewers, who are headed to the postseason this year as well. But the move did electrify the A’s, giving them a cleanup hitter and building block that made their postseason run possible.

Davis not only leads the majors in home runs this season, but is second in the majors with 123 RBIs. He’s hit 19 of his home runs in the seventh inning or later, including two walkoffs and two tiebreaking shots in extra innings. In a way, he’s come to embody the unlikely A’s, who weren’t expected to do much but have flourished beyond expectations with a flair for the dramatic.

“It’s tough to get that type of player that really enjoys being here and I know he’s that guy,” Melvin said. “He’s been instrumental in everything we’ve done the last few years and significantly this year.”

Said Canha: “He energizes us a lot. It’s good to have a guy like him in your lineup where he can inject some energy to you. A long baseball season, you need guys like that and he gives us that spark from time to time.”

Prospect-for-veteran trades are always risky. Sometimes the prospects turn out to be better than the veteran. Others times the veteran ends up being better even in the long run.

In the A’s case, they got themselves a winner.

“It was a business move,” Davis said. “I wasn’t mad at them for trading me. It’s worked out for the best. I’m grateful.”

So, undeniably, is Oakland.