Kaepernick's late-season reliance on Crabtree can't be overstated. In the 10 games in which Kaepernick started, Crabtree was targeted a whopping 92 times compared to 39 apiece for Vernon Davis and Randy Moss.
Crabtree finally emerged as a big-time NFL receiver under Kaepernick, showing elite hands and run-after-catch ability. He averaged seven receptions, 103 yards and nearly a touchdown over the final eight games of the regular season and playoffs. Crabtree's 16-game averages when Kaepernick received starter's snaps projected to 96 receptions, 1,382 yards and 13 touchdowns. Those kind of numbers will leave players, coaches and even fantasy football fans wondering what Crabtree's injury means.
Now that we've established Crabtree's dominance with Kaepernick, the question is what the 49ers will do to make up for his absence. With Mario Manningham and Kyle Williams returning from anterior cruciate ligament injuries, the 49ers' depth chart is shallow. Let's take a look at the options.
» The Anquan Boldin trade suddenly takes on more importance, though we shouldn't expect a repeat of his postseason dominance on a new team. Boldin can win with physicality, but he's another year older after struggling to separate from coverage the past couple of seasons.
» Kaepernick will have to get more comfortable throwing to Vernon Davis, who's now the most dangerous weapon in the 49ers' passing attack. Davis concentrated on blocking once Crabtree emerged as Kaepernick's go-to receiver, but he's just 19 games removed from a three-game stretch in which he torched the Atlanta Falcons, New Orleans Saints and New York Giants for 18 receptions, 410 yards and four touchdowns to close out the 2011 season.
» The 49ers have young talent in 2012 first-round draft pick A.J. Jenkins and 2013 fourth-rounder Quinton Patton, but are either of them ready to join Boldin in the starting lineup? Might the team consider bringing back Randy Moss or Braylon Edwards? The available free-agent list is sparse behind Brandon Lloyd, featuring the likes of Laurent Robinson, Ramses Barden, Steve Breaston, Devery Henderson and Austin Collie.
» If general manager Trent Baalke opts to go the trade route, he's armed with a bevy of extra draft picks. Nate Washington of the Tennessee Titans was available earlier in the offseason and probably still could be had for a mid- to late-round pick. Heavy contracts would stand in the way of a Santonio Holmes or Robert Meachem trade.
No matter how the 49ers move to replace Crabtree, his absence will be felt, even on a deep and talented roster. The silver lining is San Francisco's creative coaching staff has proven capable of winning with a variety of styles.
Follow Chris Wesseling on Twitter @ChrisWesseling.