The past few days have not been kind in health for two of baseball's premiere franchises. The Red Sox lost 2011 AL MVP candidate Jacoby Ellsbury for at least six weeks to a subluxed shoulder, and Giants closer Brian Wilson might be looking at a lost season due to elbow surgery. The Yankees have been fortunate to avoid significantly crippling injuries since Derek Jeter and Mariano Rivera debuted with the team in 1995, with 2008 being the only exception (It is not a coincidence that this was the only year in the 17-year stretch that they missed the playoffs. Thanks for that, Jorge Posada's shoulder.) The injury histories of Jeter and Rivera have been noticeably light over the years, and keeping them healthy (especially in comparison to other teams) has helped the Yankees excel.
Rivera has spent time on the DL four times, but they all occurred within a little more than a year of each other. The 2002 season was the only season of Rivera's career other than his first year that he he appeared in less than 50 games (in his first year, he was predominantly a starter and rode the AAA Columbus/New York expressway for most of the year). The '02 season saw him miss some time at various short periods throughout the campaign--he spent time on the 15-day DL with a groin strain from June 10-25 and a shoulder strain from July 21st through August 8th. A re-aggravation of the should strain forced him to miss time again from August 18th through September 20th. Setup man Steve Karsay filled in for him quite well during his absences and fortunately, the Yankees did not miss a beat, as they went 36-25 in Mo's absence.
The primary negative side effect of Karsay's effectiveness was that it compelled manager Joe Torre to use him more often, and by the end of the season, he had pitched a startling 78 games and 88 1/3 innings. In September, his weariness showed as he pitched to a 4.63 ERA, and in the ALDS against the Angels, he was smacked around in two of his appearances. Karsay's shoulder was shredded, and major shoulder surgery forced him to miss the next season and a half of his four-year, $21 million contract. He did not pitch again until September '04, and he was never the same pitcher after the '02 season. Rivera's injury had lasting side effects beyond simply him not pitching, and the Yankees were quite lucky to never have him miss much time beyond the '02 season (save for April '03). Relievers continued to be burned by Torre's bullpen strategies, but Rivera was never really a part of the problem again. The Giants will have a tough task finding the right balance in bullpen management to fill Wilson's role, and hopefully they will find a way through it. Rivera's pure health has enabled him to pitch in 1,046 games since 1995, a figure that is 13.6% (125 games) higher than any other reliever in baseball. Despite his many accolades, that is a number that is as important as any he has established during his 18 years in the Bronx.
Jeter has somehow only landed on the DL twice in his 18-year career. He dislocated his right shoulder on Opening Day 2003 in a violent collision at third base with Blue Jays catcher Ken Huckaby, but he somehow only missed 42 days. April '03 was a weird time for the Yankees, as Rivera was on the DL himself with a groin strain (to date, the last time he was on the DL). Thus, fans got to see Erick Almonte at shortstop and Juan Acevedo close out games. Almonte hit .263/.327/.358 in Jeter's absence, but showed little power at the plate and was somehow even worse in the field than Jeter (-41.3 UZR/150 and 12 errors in less than 250 innings). Acevedo was getting saves, but he sure looked ugly doing so. He gave up nine runs in ten innings during April, an ERA of 8.10. The Yankees wasted little time getting Rivera back into action after April 29th, and Acevedo did not even last through June with New York. Because the injuries occurred early in the season though, there were few major repercussions from the injuries. Jeter's only other time on the DL was last year, when he missed half of June with a calf injury just prior to reaching the 3,000 hit milestone. Eduardo Nunez filled in and played well while Jeter was out, and Jeter's absence was inconsequential during the Yankees' run to the AL East title. Jeter has played 2,434 games with the Yankees, a mark that also dwarfs his contemporary shortstops. Discounting third base convert Alex Rodriguez, Jeter has appeared in 11.6% more games (254 games, a full season and a half) than any other shortstop since '95. He might struggle defensively at the position, but the fact that he has been out there almost every day for 17 years certainly means a great deal to the Yankees. It is even more difficult to replace everyday position players than pitchers, and Jeter's health has afforded the Yankees an invaluable luxury.
If Rivera and Jeter had missed time like Ellsbury and Wilson are facing, there is no way of knowing how the Yankees' success during the '90s and 2000s would have changed. Maybe they would have found a way to win with substitutes like Almonte and Acevedo anyway. Regardless, their everyday impact on the game was valued, and the Yankees surely appreciated their ability to stay healthy when they did not have much depth. The Yankees of 2012 are in a better position to handle missed time at these positions, as better young players await in the wings in case of an injury to Jeter or Rivera. Nunez and David Robertson are superior replacements than Almonte and Acevedo were, and that is a testament to the revival of the Yankees' minor league system.