Stop-gaps. Teams hope these players can step in if a regular sustains an injury, or simply needs to sit for a spell to mull missed assignments. Often these players contribute very little, even on special teams. Sometimes they sub in on special packages, such as goal line, or short-yardage situations. No one expects these subs to develop into long-term impact players, and folks are generally happy if they don't mess up too badly. Usually, veterans on their way out fill these slots. An example from last season: Leonard Davis. Teams would prefer to have more of the other kinds of depth, but, given the injury hazards, most organizations, realistically, need to settle for a few stop-gaps. Occasionally, like Deion Sanders for the 1994 Niners, these players exceed stop-gap status and become one-year wonders.
Contributors. Teams need as many of these guys as they can get. Where do they contribute? As special-teamers, backups, and part-time starters. Ideally, one would like these players to excel not only on special teams, but to provide quality playing time when starters need rest. Indeed, sometimes they blur the distinction between backup and starters, for instance Delanie Walker (best wishes in Tennessee, versatile one) or Chris Culliver. As all 49er fans know, the current special teams need boosting. While stop-gaps often sign as free agents or arrive via trade, teams traditionally add these contributors during the middle and late rounds of the draft, or even as undrafted free-agent signings.
Replenishers. Every team hopes to stockpile as many of these players as possible. Every fan invests dreams of future success in these guys, even if they don't always pan out. These players, however they arrive, usually in the early-to-mid rounds, may not start right away, but they catch the eyes of coaches and fans alike, and often, at a young age, work and/or dazzle themselves into more playing time, and, eventually, become starters. These players provide true quality depth, not only in and of themselves, but because they permit teams to let more expensive veterans leave in free agency. NaVorro Bowman provides a penultimate example: drafted in the third round in 2010, he flashed so much ability that the 49ers let Takeo Spikes walk the following season, and installed Bowman as starting inside linebacker. Mr. Bowman's subsequent play testifies to the importance of stocking the depth charts with potential young starters.
True depth does not just mean names on a roster, but quality players capable of contributing now, and starting later. The 49ers 2012 draft has so far not provided much in the way of replenishers, although some of last year's rookies, particularly the injured, may yet pan out. But the 2013 49ers cannot afford two consecutive drafts bereft of replenishers, and short, too, of genuine contributors. For that reason, the upcoming draft looms as especially important, both in terms of salary-cap implications, and as a source of replacement talent.
