By reputation, Coors Field is the most unfavorable ballpark for Major League pitchers. The physical toll of maintaining a rest-and-recovery routine at altitude is cited as one major reason why.
Yet the Rockies' rotation has been remarkably durable this year, if not always effective. Colorado manager Bud Black has used the same five starting pitchers all season. The defending World Series champion Astros -- with a rotation that could be among the best ever -- are the only other team for which that is true. 
Meanwhile, Dodger Stadium is known as a pitchers' haven. The Dodgers had the Majors' best rotation ERA en route to a World Series appearance. Even after the departure of Yu Darvish, future Hall of Famer Clayton Kershaw was expected to headline a similarly dominant group in 2018. 
Instead, injuries have decimated the Dodgers' staff. Kershaw is on the disabled list for a second time this season, and Los Angeles has used 11 starting pitchers. The Rays are the only team to need more, and that is because of their avant-garde practice of opening games with relievers.
In other words: Very little has gone according to plan this year in the National League West. The fourth-place Rockies are 3 1/2 games behind the first-place D-backs in the Majors' most compact division. The Dodgers and Giants are tied for second at 2 1/2 games back of Arizona.
Moves at the July 31 non-waiver Trade Deadline could have an outsized effect in such a close race, but there's little consensus as to how the coming weeks will unfold. 
The Giants and Dodgers have two of the Majors' three largest payrolls, which could signify one of two paths: They could add to their investments in veteran rosters, in an effort to extend their windows to win the World Series. Or they could operate more cautiously, preferring cash-neutral trades in an effort to avoid Competitive Balance Tax penalties. 
For example, while Baltimore's Manny Machado is a dream fit for the Dodgers following Corey Seager's season-ending injury, it's difficult to imagine the Orioles would agree to pay all of Machado's remaining salary in a trade with Los Angeles when suitors with greater payroll flexibility may not insist on them doing so. 
The Giants may be content to keep their current roster intact, especially if starters Johnny Cueto and Jeff Samardzija return before the All-Star break, which is possible. 
The D-backs made the division's first notable regular-season move with last week's acquisition of outfielder Jonathan Jay from the Royals. Jay immediately became Arizona's leadoff hitter, starting all three games of the D-backs' weekend sweep of the Rockies at Coors Field. 

In a Friday interview with MLB.com, D-backs general manager Mike Hazen indicated he's likely to evaluate starting pitchers Shelby Miller and Robbie Ray after they return from the disabled list -- likely later in June -- before pursuing upgrades to the pitching staff. 
Arizona could focus its attention on relievers, since closer Brad Boxberger has struggled when pitching on three consecutive days. But the bullpen may improve organically, if the arrivals of Miller and Ray push the team's fourth and fifth starters into relief roles.
"You're always going to be looking at pitching, [whether it's] the bullpen or a starter, depending on how everything progresses," Hazen said. "Hopefully, getting Miller and Ray back will solidify that part of our team, and then we'll see what the fallout of that will be with the bullpen and where we might go from there." 

The next NL West trade could come from Colorado to address a crumbling bullpen that is threatening to undermine the team's season. Despite committing more than $100 million combined to free agents Wade Davis, Bryan Shaw and Jake McGee during the offseason, the Rockies' bullpen has a 5.22 ERA entering Monday's games, which is 27th in the Majors.
"We're going through a tough time with the 'pen," Rockies GM Jeff Bridich told MLB.com. "There have been a small handful of guys in the 'pen who have been really good and have done their job to the expectations. A couple guys unexpectedly have struggled, and the struggles have lasted longer than they have ever struggled in years previously. We just need to keep working together, because they're talented. It's not like they've lost talent. 
"Fortunately, we've been healthy. Other than [Adam] Ottavino -- who's on his way back -- we've pretty much had our health. Hopefully, it stays that way. And if it does, then I think we'll have a normal type of Trade Deadline process. Since relievers usually are the types of guys talked about at the Trade Deadline, we'll probably do our due diligence there. But we're still a long way from that specific date. There's a lot of games to be played and a lot of stuff that could still happen."

In the meantime, the Rockies will ask their rotation to extend deeper into games and limit the bullpen's exposure. Jon Gray, who starts the Rockies' next game on Tuesday in Philadelphia, is the Colorado starter who most illustrates that need. Gray started last year's NL Wild Card Game and on Opening Day, but he has a rotation-worst 5.66 ERA. 
"When he's been good, he's been really good. When he's been bad, it's been tough to watch," Bridich said. "We need him to step up. This is his third full season at this level. There are still lessons he's learning. But he's no longer a young kid in this league, at this level. He needs to step up, and we need to help him find a way to become more consistent. 
"I'm not sure there's a ton left for him -- if anything -- [to learn] at the Triple-A level. If at some point it becomes obvious he would need a mental breather, physical breather, or both, that would be an option. But the hurdles are here. He's got to figure this out at this level. That's just the way it is. It's where he's at in his career." 
Today, Gray's team finds itself in the Majors' most wide-open division race, one waiting to be shaped by teams' trade activity -- or lack thereof -- between now and the final day of July.