The Washington Nationals were swept by the Chicago Cubs in a four-game series that concluded on Sunday. Even though the Nats were able to score 16 total runs against arguably baseball's best pitching staff (the Cubs have a combined 2.48 team ERA, which is first), there were plenty of opportunities to pile on the runs.

This is especially true considering Bryce Harper was virtually always on base during the series -- including all seven of his plate appearances on Sunday.

Chicago can thank Washington's manager Dusty Baker for leaving the struggling Ryan Zimmerman in the four-hole for the entire series, and especially during Sunday's finale. Because he's a key reason the Cubs were able to get the sweep.

The Struggle Is Real for Zimmerman

Zimmerman left a whopping 14 runners on base during Sunday's game. Yes, you read that correctly. Not 14 for the series, but 14 for just Sunday's contest, which has only happened three other times over the last 60 years. And each time required at least a 15 inning game, or two more innings than Zimmerman played Sunday. The Cubs gave him plenty of opportunities to beat them, and minus a run-scoring double in the third inning, Zimmerman performed exactly as they were hoping he would.

Zimmerman has played 27 games this season and has hit fourth in all of them. According to Baseball Reference, the average slash for a hitter batting cleanup this season is currently .256/.328/.457 with a .785 OPS. These numbers are certainly not eye-popping, but they're significantly better than what Zimmerman is doing at the plate. He's hitting just .227/.283/.327 with a .611 OPS.

Harper has hit third in every game he's started this season, meaning that for every game Zimmerman has been in the lineup, he has been Harper's "protection." With a far superior option hitting behind Zimmerman in the lineup, it's time Baker makes a change.

Former Foe Turned Friend

Signed this offseason as a free agent, former New York Mets second baseman Daniel Murphy has been one of baseball's hottest hitters since the season began. He's currently slashing .398/.441/.661 in 127 plate appearances and has primarily served as the Nats' fifth hitter in the lineup. Based on how he's performed at the plate compared to Zimmerman, it's a wonder why he hasn't been moved up in the order sooner.

Murphy isn't just dominating Zimmerman at the plate. His current numbers also stack up among baseball's best. His .467 wOBA and his 1.102 OPS both rank second best, while Zimmerman's .271 wOBA and .611 OPS both rank 27th worst. To further drive the point home about how much better Murphy has been this season, his .661 slugging percentage is better than Zimmerman's OPS (.611).

The argument that having Harper and Murphy -- who are both lefties -- hit back-to-back instead of having Harper protected by a righty doesn't hold any weight at the moment. Murphy's batting average (.444 to .385) is better when facing lefties this season, and his wOBA (.461 to .469) is just slightly worse.

When asked about keeping Zimmerman as the team's cleanup hitter, Baker offered an honest take.

He left Zimmerman in the four-hole in Monday's game against the Detroit Tigers, and Zimmerman provided more of the same results. He went 0-for-4 and left another 5 runners on base, including after Harper was walked to load the bases in a tie game in the bottom of the 7th. Murphy, meanwhile, went 2-for-4 with a home run and 3 runs batted in.

The argument to move Murphy into the cleanup spot is an easy one, but a more difficult option might actually be to take Zimmerman out of the lineup completely.

From Cleanup Hitter to Riding the Pine

I can't think of a scenario in which an everyday four-hitter was removed from the lineup for a bench player, but given who Baker has available, it's worth his consideration.

Clint Robinson saw regular action for the first time in his career last season because of injuries to Zimmerman, and he didn't disappoint. His 2015 numbers were superior to Zimmerman's in several categories.

Zimmerman's slugging percentage was the only category above in which he performed better than Robinson last season. Robinson only has 32 plate appearances this season, but owns a .222 Isolated Power, has 8 RBI (just 4 less than Zimmerman in 88 fewer plate appearances), and surpassed him in home runs after doing this Monday night:

I'm not suggesting moving Robinson into the cleanup spot, but giving him additional at-bats while taking some away from Zimmerman might not be the worst idea.

Regardless, it's time for Baker to move Zimmerman down in the order and preferably allow Murphy to hit cleanup.

Having Murphy hit behind Harper doesn't mean that other clubs still won't choose to implement the same strategy as the Cubs (the Tigers walked him twice on Monday) but, in theory, it will give the Nationals a better chance at taking advantage of driving Harper in.

Baker said he wasn't fair weather, but with Zimmerman's performance remaining in the gutter, his "couple days" are quickly evaporating.