When you watch the replay of Scott Cousins' collision with Buster Posey, you see Posey setting up slightly in front of the plate. While I wouldn't call it a dirty play, it's clear Cousins had room to slide around Posey to the back of the plate. But it's unfair to expect Cousins to make a split-second decision to determine if Posey is a few inches that way or this way, or whether he'll catch the ball or drop it. It was an unfortunate play, a play that baseball has allowed to happen for far too long.
Anyway, Buster Olney did a terrific job summing up the issues of the home-plate collision, so I thought I'd take a different direction and look at some of the game's most irreplaceable players.
For example, I wouldn't place Adrian Gonzalez on that list. As he good he is, the Red Sox could move Kevin Youkilis over to first base and Jed Lowrie to third base, with Marco Scutaro or Jose Iglesias playing shortstop. Yes, they'd lose offense, but the defense would actually improve. Miguel Cabrera is the centerpiece of the Detroit offense, but they could play Victor Martinez at first and they have other DH options. It wouldn't be a season-ruining blow. The Rays, for example, survived several weeks without their best player; heck, we're nearly a third of the way into the season and they're doing OK even though Evan Longoria hasn't done much at all. The Rays survived Longoria's injury and slow start due to having adequate infield help in Sean Rodriguez and Elliot Johnson.
As for Posey, his loss is certainly huge. With Pablo Sandoval currently on the DL, and Andres Torres missing much of the season so far, he's been their only effective offensive player for a large portion of the schedule. The Giants are last in the NL in runs scored as is. While Eli Whiteside is a decent backup, he's a replacement-level catcher. With Posey projected as a four- or five-win player over the full season, you could be looking at a three-win differential over the rest of the season.
Here are five other irreplaceable players (position players only):
Troy Tulowitzki, Rockies: With the Rockies struggling to score runs and Carlos Gonzalez not hitting like last season, losing Tulo's bat (and defense) would be devastating. He's played 47 of 48 games this season and the Rockies don't even carry a legitimate backup shortstop on the roster.
Carlos Santana, Indians: Cleveland's version of Posey, a young catcher who anchors the middle of the order. Santana has more offensive support around him than Posey, but backup Lou Marson is even less effective offensively than Eli Whiteside, with a career .210 average.