The Dodgers entered this week's showdown series against the Nationals with the best team ERA in Major League Baseball. However, executives around the game expect Los Angeles to pursue pitching upgrades -- starters and relievers -- before the July 31 non-waiver Trade Deadline.

The reasons:

1. The rotation, while effective, has durability concerns

Among the seven pitchers to start at least one game for Los Angeles this season, six have spent time away from the active roster due to injury or assignment to the Minors.

Rich Hill has had two stints on the disabled list due to a blister on the middle finger of his left (throwing) hand. Kenta Maeda had a tight left hamstring, Brandon McCarthy a dislocated left shoulder, Hyun-Jin Ryu a left hip contusion. Lefty Alex Wood is idled by an inflamed joint in his throwing shoulder. Julio Urias is pitching well, albeit with a high walk rate, at Triple-A Oklahoma City.

The group of six has combined for one Major League regular season of 200-plus innings -- by McCarthy in 2014. And then there is Clayton Kershaw , who's done it five times.

Thus, the Dodgers must ask themselves: Are they comfortable with the risk that two of the aforementioned starters won't be available in October due to injury? The group's collective history suggests it's reasonable to expect that level of attrition.

2. Kershaw turns 30 in March

Kershaw is as brilliant as ever, ranking among the Majors' top three in ERA and WHIP once again in 2017. But it's worth pointing out that, according to Baseball-Reference.com, Pedro Martinez is the closest historical comparison to Kershaw through this age. And Martinez won his final Cy Young Award in his age-28 season.

There's no way of knowing if Kershaw will follow Martinez's trajectory after turning 30, but the fact remains: Los Angeles cannot afford to squander opportunities to win the World Series while Kershaw is at the height of his powers.

For the Dodgers to maximize their chances at winning a World Series title for the first time since 1988, they'd be advised to have four trusted starting pitchers -- not three -- on their National League Division Series roster.

Kershaw has started on short rest in Game 4 of the NLDS in each of the past four postseasons. On the two occasions when Los Angeles advanced to the NL Championship Series, in 2013 and '16, an exhausted Kershaw was the losing pitcher in the season-ending defeat.

October is a small-sample-size universe, so the Dodgers would be wise to conclude that having Kershaw start on short rest from the NLDS onward is not sustainable as a championship-winning strategy.

3. The Dodgers have the currencies to pursue almost anyone

The Dodgers have the prospect depth and vast financial resources to be part of any trade conversation in the Majors this summer. And so they won't limit themselves to the rental collection that includes Royals left-hander Jason Vargas and possibly Rangers right-hander Yu Darvish .

Gerrit Cole , Chris Archer and Ervin Santana -- to name only three -- all are under control beyond the end of this season and will potentially be available over the coming weeks. And A's right-hander Sonny Gray is sure to be linked to the Dodgers, given the Oakland ties of Los Angeles general manager Farhan Zaidi. Justin Verlander 's postseason pedigree makes him an intriguing name, but his $28 million annual salary through 2019 is problematic -- especially in light of his 4.63 ERA and recent groin injury.

If Urias is off limits in those discussions, then Double-A right-hander Walker Buehler (the Dodgers' No. 4 prospect) could be pivotal in any successful offer from Los Angeles -- depending on how aggressive the Dodgers prove to be.

4. The Dodgers' need for a left-handed reliever is apparent

Grant Dayton was a revelation for the Dodgers last year, advancing from Double-A to assume a key role in the postseason bullpen. But his numbers have regressed across the board in 2017, and he's currently the only healthy left-handed reliever on Los Angeles' roster.

It's possible that the left-handed Wood will join the bullpen during the playoffs, but the Dodgers must acknowledge the possibility that he'll be needed in the rotation. And so they're formulating a wish list of southpaws that includes the Pirates' Tony Watson and the Padres' Brad Hand.

Watson, a potential free agent after this season, and Hand, who is arbitration-eligible through 2019, also are of interest to the Nats -- the Dodgers' opponent this week and perhaps again in October.