The D-backs shocked the baseball world by winning the National League last year, but going into the 2024 season, there are bound to be some who consider Arizona's improbable run a one-off occurrence.

Arizona made it abundantly clear that the goal in 2024 is a World Series championship by swooping in and landing left-hander Jordan Montgomery to join a starting rotation headlined by 2023 All-Star and NL Cy Young Award finalist Zac Gallen.

Montgomery and the D-backs agreed to a one-year, $25 million contract with a vesting option just two days before Opening Day, a source told MLB.com's Mark Feinsand. The move adds to the excitement surrounding the defending NL champs, whose World Series run last fall was their first since 2001.

The aforementioned Gallen, one of the faces of the club along with reigning NL Rookie of the Year Corbin Carroll and slugging first baseman Christian Walker, said he's "pumped."

"The front office went out there and added Jordan Montgomery," Gallen said on MLB Network Radio on Wednesday. " ... We've seen his bill of work and we know what he can do, so we're excited to get him in the clubhouse and get him in our culture and see him go to work."

When Gallen said the D-backs know what Montgomery can do, he was hearkening back to October, when the left-hander helped the Rangers win the franchise's first World Series title over Arizona.

Overall, Montgomery owns a career 3.68 ERA over seven Major League seasons. The 31-year-old was among the top names on this offseason's free agent market after posting a 3.20 ERA in 32 starts between the Cardinals and Rangers last year, including a 2.79 mark in 11 starts down the stretch for Texas.

The acquisition of Montgomery bolsters a rotation that also includes Merrill Kelly, Tommy Henry, Brandon Pfaadt and Ryne Nelson. The D-backs also signed left-hander Eduardo Rodriguez in December, though he is currently sidelined with a lat strain.

Beyond helping the D-backs on paper as they look to prove they aren't a one-year wonder, Gallen said the impact on the clubhouse is significant.

"It gives everyone a lot more confidence, knowing that the front office and ownership is backing you," he said. "They're doubling down. They're going to invest in our team. I think it gives the guys in the clubhouse confidence to know that we are good enough and we have a product that [the front office] can invest in."

On the eve of Arizona's season-opener against the Rockies at Chase Field, Gallen underscored how highly anticipated this moment has been since the D-backs fell short of the ultimate prize last fall.

"We're really excited to see how this season takes shape for us," he said. "We're obviously a little bit bummed that we didn't finish the job [last year] ... There are a lot of guys that feel like we still have something to prove, which we do. To do it one year – there are one-hit wonders all the time."