For a time yesterday, it appeared that the biggest baseball injury of the day would be Giants Third Baseman Pablo Sandoval’s broken hamate bone. That was, until the early evening in Kansas City.

Many relief pitchers will spend their time during batting practice catching fly balls. Yankees closer Mariano Rivera has made a 17 year habit of “shagging” fly balls before games. Until last night, no one really noticed.

While running back toward the centerfield wall, Rivera caught his foot on the warning track and twisted his knee. He fell to the ground, wincing in pain, clutching the knee. He was carted off the field and later diagnosed with a torn ACL. He will miss the rest of the 2012 season, one that many believe would be his final in Major League Baseball.

If it is, Rivera will retire as the greatest relief pitcher in history. His 608 career saves is the most in baseball history. For Rivera, though, it’s his more advanced statistics that tell the story. As a relief pitcher, his 58 wins above replacement put him as the 58^h most valuable pitcher in Major League Baseball history. The next closest relief pitcher to Rivera is Trevor Hoffman. He ranks 260^th. Rivera is second all-time in WHIP (Walks+Hits/Innings Pitched). He is 5^thall-time in K/BB ratio (Strikeouts/Walks). He is the career leader in adjusted ERA+ (don’t ask).  He is 4^th all-time in WPA (win probability added). He is simply the greatest relief pitcher we have ever seen. And that is to say nothing of his postseason dominance, in helping the Yankees win 4 World Series titles.

The knee injury is the most unfortunate way that the 42 year old pitcher’s career could end. There is a chance that Rivera could decide to come back next year. I have my doubts that a 42 year old will want to rehab from an ACL injury in time to pitch again next year. But we shall see.

In the interim, the Yankees will likely give the 9^thinning duties to current setup-man David Robertson, who has been excellent in his role, but is unproven as a closer, especially given the shoes he’ll have to fill.

Batting third in just his fifth Major League game, Bryce Harper drove in the game-winning run last night for the Nationals as they beat the Arizona Diamondbacks 2-1 to earn a series victory.

The Diamondbacks could not solve Nationals starter Ross Detwiler early in the game and the young lefty only allowed 3 hits in the game. The bullpen (Ryan Mattheus, Tyler Clippard, and Henry Rodriguez) pitched 2 2/3 innings of  perfect baseball to preserve the victory.

The Nationals will welcome their unfriendly rival from Southeastern PA tonight for what should be a contentious three-game series. Your weekend pitching matchups:

Friday: Kyle Kendrick vs. Stephen Strasburg (7:05/MASN (locally),MLB Network (nationally))

Saturday: Vance Worley vs. Gio Gonzalez (1:05/MASN)

Sunday: Cole Hamels vs. Jordan Zimmermann (8:05/ESPN)

The Phillies enter the series 3.5 games behind Washington.

MLB: Phillies @ Nationals (Sunday at 8:05 p.m.)- A huge test for Nationals fans. Yes, you read that write. It’s the team’s first ESPN game in 4 years. They must take back the park.

NBA: Hawks @ Celtics (Tonight at 7:30 p.m.)- A crucial game for both clubs. Especially the Hawks who can’t afford to give additional momentum to Boston.

NHL: Rangers @ Capitals (Saturday at 12:30 p.m.)-See above. Substitute “Capitals” for “Hawks” and “New York” for “Boston.”

Soccer: Chelsea vs. Liverpool (FA Cup Final) (Saturday at 12:15 p.m.)-Two of the premier (see what I did there?) clubs in English football battle for the oldest cup championship in the world.

Horse Racing: Kentucky Derby (Saturday at 6:00 p.m.)-Horses run around a track. People in Kentucky get super drunk and bet on those horses. Hats.

A safe weekend to the readers. You all need a nickname. Discuss!