DENVER -- Jeff Hoffman's historic two-inning collapse in Tuesday night’s 9-3 loss to the D-backs at Coors Field illustrated how much the Rockies’ foundation of starting pitching has crumbled this year.

Hoffman, summoned from Triple-A Albuquerque because Jon Gray was scratched with left ankle soreness, became the first pitcher in club history to give up four home runs while pitching two or fewer innings. The key to the 2015 trade that sent star shortstop Troy Tulowitzki to the Blue Jays, Hoffman, who gave up seven runs on six hits, has a 7.81 ERA in nine starts for the Rockies this season and a 6.31 ERA in 46 career appearances (31 starts).

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“I just go out there every day and try to execute a game plan, that’s it,” Hoffman said. “Whether that happens or not, that’s on my ability to execute a pitch. Tonight, I couldn’t.”

Hoffman gave up homers to Jarrod Dyson, Christian Walker and Nick Ahmed in a five-run first, with the latter two each hitting a two-run blast. David Peralta then hit a two-run homer in the second. The Rockies couldn't rally back as they left the bases loaded in the first and left runners on the corners in the fourth.

But Hoffman’s tough night -- which dropped the Rockies to a National League-worst 13-33 from June 21 -- started this past Thursday, when Gray slipped going down the dugout stairs early in his start at San Diego.

The Rockies’ biggest joy came when debuting catcher Dom Nunez homered for his first Major League hit in the eighth. Bench coach/catching instructor Mike Redmond presented him with a baseball representing the seventh time in the 27-year-old franchise’s history that a player has homered in his debut. Trevor Story on Opening Day 2016 was the last before Nunez.

“The main thing I thought honestly was you put the swing that you want to put on it and good things happen,” Nunez said. “Rounding second, everything was pretty blurry at that point.”

The Rockies saw their starting-pitching issues exposed when they again had to dip into their depth this season.

In 2017, manager Bud Black used skipped starts and options to the Minors to protect the four rookies among his seven pitchers who made at least 10 starts. In '18, Kyle Freeland, who became an NL Cy Young Award candidate, German Marquez, Tyler Anderson and Gray all made 30 or more starts, and Rockies starters led the NL in innings pitched.

But this year, Freeland struggled early and was demoted to Triple-A, Anderson pitched through early-season pain before undergoing season-ending left knee surgery and righty Chad Bettis proved better in relief than starting. While Marquez and Gray have shown the most consistency, the Rockies have received little from their depth starters, including Hoffman.

Arguably the best of the bunch is righty Antonio Senzatela, who was 8-7 with a 6.29 ERA before being optioned to Albuquerque on July 21 in an attempt to stem a pattern of starts bordering on brilliance followed by episodes of futility. 

Righty Peter Lambert is going through the ups and downs in his rookie season. Righty Chi Chi Gonzalez was sent down to accommodate Hoffman’s recall. In an attempt to find depth, the Rockies have converted lefty reliever Chris Rusin -- cast out of the Rockies’ bullpen when designated for assignment June 7 -- to starting at Albuquerque.

“You’d like to think a year of experience with a number of guys would get them in a better place, but that doesn’t seem to have happened this season,” Black said. “We’ve stayed relatively healthy, with the exception of Anderson … you look around the league and a lot of teams have used a lot more than [nine]. With that, the performance from those has been a stark contrast to last year.”

For two seasons, the Rockies’ rotation pitched well enough not to dig into their depth.

But Hoffman’s performance Tuesday showed how when the Rockies need reinforcements, they’re merely in the depths of trouble.