DENVER — Those who fancy Wins Above Replacement, which is all the rage these days, might be interested to know that the Giants’ most valuable player under the Baseball-Reference formula is rookie pitcher Dereck Rodriguez.

That should surprise nobody who has watched more than a handful of games in 2018. Rodriguez not only has been the most successful Giant this season, his starts have become destination viewing.

Maybe not the way they were with Tim Lincecum back in the day, but hey, Rodriguez has the hair, and he’s getting there.

Fans counting down the final days of what looks to be another losing season, further scarred by Tuesday night’s 6-2 loss to the first-place Rockies, can only shut their eyes and imagine the damage that Rodriguez could do on a team that consistently hits and protects late leads.

The Giants have done neither well of late, especially at Coors Field, where they lost for the 17th time in their past 19 games despite Rodriguez holding Colorado to a David Dahl solo homer in six innings.

San Francisco took a 2-1 lead in the seventh on Gorkys Hernandez’s 15th home run. The Rockies obliterated that lead in the bottom half, scoring five times, three on a Carlos Gonzalez triple against Ty Blach, who was brought in specifically to face him.

“It’s a shame we can’t hold on to these games, especially when he’s pitching,” manager Bruce Bochy said of Rodriguez.

The bullpen is having a hard time holding on to anything right now. The relievers were a strength for a good part of the season and seemed to find a rhythm.

But with Tony Watson giving away a hard-fought lead Monday night and Reyes Moronta allowing Ryan McMahon’s tying homer in the seventh inning Tuesday, the Giants technically absorbed their 28th and 29th blown saves, worst in the majors.

Five walks, two intentional, punctuated the five-run Rockies seventh, which sealed the Giants’ fourth straight loss.

They are 68-72. Even the modest goal of a .500 finish now looks like a long shot. The Giants need to go 14-8 to go home a “winning team.”

“That’s what we’re looking for, a winning record, the managers, the coaches and the players,” Hernandez said after catching Andrew McCutchen and Evan Longoria for the team lead in homers at 15.

Whatever the final record, the Giants’ impotence at the plate (caused only partly by injuries), the months-long struggles of core players who are signed long-term and the fading bullpen should force team executives to ask themselves hard questions:

Are the Giants really a couple of trades and signings away from contending in 2019? Can they really turn this around long term without trading Madison Bumgarner, their best movable asset? Are Brandon Belt, Brandon Crawford, Joe Panik and Evan Longoria coincidentally struggling in a year in which most were hurt? Or is this the future?

The overriding question about Rodriguez is, how good can he be? In his past 12 games he has a 1.72 ERA and he is showing no signs of wearing down in his first big-league season.

He is pitching with a confidence bordering on cocky — a good cocky. Some pitchers are afraid to throw curveballs at altitude. Not Rodriguez. He threw 18 of them, his best pitch as he returned to the park where he made his big-league debut May 29.

MORE: Giants call up just-acquired infield prospect Avelino

“I forgot how fun it is to pitch here,” Rodriguez said, echoing comments said by no sane person ever. “I just love the mound here.

“I felt like this was going to be a test for me today, facing the first-place team, here in Colorado, a big hitters’ park. I put a challenge on myself and I executed.”

Henry Schulman is a San Francisco Chronicle staff writer. Email: hschulman@sfchronicle.com Twitter: @hankschulman