The Arizona Diamondbacks believed that J.D. Martinez, even as a half-year rental, could be a game-changer when they dealt three minor-league prospects to acquire him from the Detroit Tigers.

Backing slugger and MVP candidate Paul Goldschmidt with Martinez in the batting order appeared to be a winning move.

Yet, Arizona manager Torey Lovullo admits the D-backs might not have expected it to go this well.

“A lot of times you get those filler guys, those rentals that you hope are going to do something special and then they kind of fizzle and it’s not exactly what you think,” Lovullo told Burns and Gambo on 98.7 FM, Arizona’s Sports Station. “J.D. has been absolutely unbelievable for us.”

Following Martinez’s four-homer outing against the Los Angeles Dodgers on Monday night, a game in which Goldschmidt was sidelined due to an elbow injury, the right fielder is tied for 10th in MLB with 34 home runs on the year — 18 have come in 40 games with Arizona.

While his average and on-base percentage have dipped since joining the D-backs, Martinez’s slugging percentage (.688) and OPS (1.025) have both improved from his numbers in the first half of the year with Detroit.

Maybe Martinez’s seamless addition to the locker room has been more impressive than the numbers.

Together, it’s done enough to make fans wonder if the D-backs could find a way to re-sign Martinez, who becomes a free agent after this season.

“He’s been a great teammate — the things that the fans don’t get to see that I watch every single day … he’s fit in like a glove,” Lovullo said. “He just has become a part of this family in a very, very short period of time. He’s on the same page as every other Diamondback, and that’s what thrills me the most.

“I mean, the meaningful home runs, the meaningful base-hits, the things that he’s done and the types of driving runs in that he has … When you can stack him and Paul Goldschmidt together, it makes it a really, really tough lineup for any pitcher — I don’t care who they are.”

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