PHOENIX -- The D-backs and reliever Justin Martinez have finalized a five-year contract extension that begins this season and runs through 2029, the club announced on Saturday. The deal is worth $18 million, a source told MLB.com's Steve Gilbert.

Martinez, 23, posted a 2.48 ERA and 29.5% strikeout rate over 72 2/3 innings last season, his first full Major League campaign. He also picked up eight saves and is seen as a potential closer for Arizona in the near future.

“He’s got a great makeup,” manager Torey Lovullo said. “He’s got all the intangibles. We know what the arm looks like. It shows up every single night. He throws 100 mph; he continues to work on the secondary stuff to be a complete pitcher. So there have been improvements there.

“But the separator for me is his desire to get better, his ability to be a teammate, [how he] accepts that coaching and just continues to stay very, very motivated. He’s going to be a really good player for us for a long time.”

Armed with a triple-digit fastball, a changeup and a splitter, the right-hander ranked in the 90th percentile or better among qualified pitchers last season in the following categories, per Baseball Savant: average fastball velocity (100.3 mph, 100th percentile), offspeed run value (six, 92nd percentile), average exit velocity (86.4 mph, 94th), whiff rate (34.5%, 96th), barrel rate (2.8%, 99th), hard-hit rate (31.8%, 94th) and ground-ball rate (60.3%, 97th).

Martinez will receive a $2 million signing bonus and a $1.5 million salary for 2025. He’s then set to make $2 million in ’26, $3 million in ’27, $4 million in ’28 and $5.5 million in ’29. There are club options for 2030 and ’31, at $7 million and $9 million, respectively. Including escalators, the contract could reach $39 million.