Now, with the help of the former Dodgers speedster-turned Nationals first-base coach, Harper has swiped a National League-best three bases in five games and leads a team that is newly committed to aggression on the basepaths.
"It's just the confidence he instills in the guys," Harper said of Lopes during Spring Training. "Every single time you get on base, if you get a good jump and you steal a bag or even if you get thrown out, it's always, 'Keep going.'"
After ranking 27th in the Major Leagues in stolen bases last year with just over one every three games (57 total on the year), the Nationals have stolen six bases through their first six games in 2016, ranking second in the Majors and first in the National League.
The key, said manager Dusty Baker, has been Lopes' keen eye for reading pitchers' deliveries and pickoff moves. Lopes, a former second baseman, stole 557 bases in his 16-year big league career, including 77 in 1975 and 47 in '85 at 40 years old.
"There's something you can take advantage of off every [pitcher], and Davey Lopes is the best at picking that up," Baker said. "Davey sees things very few people see."
Monday's 6-4 win over the Braves was a banner day for Washington's newfound aggression. Harper and Michael Taylor stole two bases apiece, and Ryan Zimmerman helped create a run by advancing to third on a foul popup down the first-base line before scoring on an infield single.
And though Tuesday's 2-1 win over the Braves showed the risks of bold baserunning -- Taylor was caught rounding first too far and Daniel Murphy was unable to get back to first base on a popout to right field -- the Nationals will take the bad with the good.
Lopes, who was hired away from the Dodgers in November, said he had heard the Nationals were resistant to stealing in past years, but he received total buy-in from all the players this spring.
"They wanted to speed up the game," Lopes said before Tuesday's matchup with the Braves. "We wanted to go first to third. We wanted to go second to home. We wanted to advance on balls in the dirt. We wanted to advance on a mistake an outfielder made coming in charging on a ball."
Harper's basestealing has been a particularly interesting development. Often a middle-of-the-order hitter is aggressive on the basepaths early in his career, then slows down as he adds muscle and the team grows to rely on his power. For example, Mike Trout and Andrew McCutchen recorded their career-high steal totals during their first full seasons, and Joey Votto slashed his stolen-base total after he won the 2010 National League MVP Award in his third full season.
Harper had appeared headed in the same direction, slowing down after stealing 18 bags as a rookie, but he appears to have reversed course upon Lopes' arrival.
Last year, Harper didn't steal his third base of the season until his 50th game. This year, he stole his third base of the season in his fifth.
"He's a different talent," Lopes said of Harper. "Some of the good ones who become, over time, the great ones, they're always looking for something to add to their game, and he's got that mentality."
Alex Putterman is an associate reporter for MLB.com.