This growing rivalry, however, has proven to be a one-sided affair of late.
Seeking a seventh straight victory, Hamels tries to help the slumping Phillies avoid a seventh consecutive home loss and a three-game sweep at the hands of the NL East-leading Nationals on Wednesday night.
Washington (26-17) continued its recent domination of the five-time reigning division champions and extended its winning streak in Philadelphia to six for the first time in the franchise's 43-year history with Tuesday's 5-2 victory.
Ian Desmond belted his fourth homer in seven games and Jordan Zimmermann outdueled Roy Halladay, who was tagged for all five runs as Philadelphia (21-23) suffered its season-worst fourth consecutive defeat.
Winners of 13 of 16 in this series, the Nationals have held the Phillies to an average of just 2.9 runs during a 9-1 run. Their only loss over that stretch came 9-3 on May 6 versus Hamels (6-1, 2.48 ERA), who gave up five hits and struck out eight over eight innings of one-run ball.
While his performance was certainly impressive, it was Hamels' actions in the bottom of the first inning - and his subsequent admission of guilt - that dominated the headlines. The left-hander drilled Harper in the back, welcoming the 19-year-old phenom to the big leagues.
"I was trying to hit him. I'm not going to deny it," Hamels said. "That's something I grew up watching, that's kind of what happened. So I'm just trying to continue the old baseball because I think some people are kind of getting away from it.
"But I think unfortunately the league's protecting certain players and making it not that old-school, prestigious way of baseball."
Harper went on to steal home against Hamels, who was suspended five games for his actions. The two-time All-Star and 2008 World Series MVP was also harshly criticized by the Nationals organization.
"Cole Hamels says he's old school? He's the polar opposite of old school. He's fake tough," Nationals general manager Mike Rizzo told the Washington Post. "He thinks he's going to intimidate us after hitting our 19-year-old rookie who's eight games into the big leagues? He doesn't know who he's dealing with."
Washington may not be intimidated by Hamels, but it clearly hasn't had an easy time trying to figure him out. Hamels has compiled a 2.62 ERA and an 11-4 record over 21 career starts against the Nationals - tied for his highest win total against any opponent.
Hamels has been especially sharp since losing his season debut, going 6-0 with a 2.20 ERA over his last seven outings. He won his third consecutive start Friday 6-4 over Boston, yielding three runs, six hits and fanning nine in seven innings.
"I'm just doing everything I've done the past couple of years," he said. " ... It's the same sort of way I've gone out and pitched. I try to put up as many zeros as I possibly can.
"I'm focused on trying to get wins, no matter how they come. If I can plug away and do my job, then good things will happen and they have been."
Hamels will be opposed by Edwin Jackson (1-1, 3.31), who was tremendous during Friday's 2-1, 11-inning loss to Baltimore. The right-hander surrendered one run, five hits and struck out eight in as many innings.
In his only career appearance against Philadelphia, Jackson allowed five runs in five-plus frames of a 7-1 loss at Citizens Bank Park on July 28, 2010, while with Arizona.
Jackson, though, seems to have a favorable matchup against a Phillies team that's gone just 5 for 38 (.132) with runners in scoring position during its slide.
"We just don't put together enough," manager Charlie Manuel said. "We don't hit the ball good enough to win the game."
Harper, who went 2 for 5 with a triple and a pair of RBIs on Tuesday, is batting .325 with two homers and 11 runs scored in his last 10 games.
Nationals third baseman Ryan Zimmerman was a late scratch Tuesday (shoulder soreness) but is expected back Wednesday.
- Cole Hamels
- Washington Nationals
- Bryce Harper