When building an NFL team, it's important to realize that a team flush with depth is better set up to succeed over a rigorous season than a team that's top heavy. Injuries happen and depth players will be expected to step up in their absence.
A good exercise is to walk through the Patriots roster to see where their positions stand with respect to starts, rotational players, back-end depth, and those who might just be around for camp.
For example, the quarterback position has a starter in Tom Brady, a depth candidate in Jimmy Garoppolo, and a camp body in Garrett Gilbert. The tight end spot has a starter in Rob Gronkowski, a rotational player in Scott Chandler, and a depth player in Michael Hoomanawanui. These positions are fine moving forward.
A position like X receiver has a starter in Brandon LaFell, but there's no real rotational depth behind him. There are back-end depth or potential camp bodies in Brian Tyms and Aaron Dobson, but there's no one currently presenting confidence in the position should LaFell go down. This is a position that would be open to a mid-round player as depth.
Left guard is a gaping chasm that needs to be filled. Dan Connolly is a free agent, and even then his production on the field is better fitting for a rotational depth player, not a starter. There is no starter, but when you look at the roster, there's no rotational player able to fill the spot right now; there's Marcus Cannon, Cameron Fleming, Josh Kline, and Jordan Devey, all players who would be considered back-end of the roster, or even a camp body if guard was their primary position. This is a priority position that needs to be addressed.
Pulpiteers have voted and the Patriots top positions of need are at cornerback, offensive line, and defensive line. If we were to use the above groupings of talent, we would consider the following:
Cornerback: The Patriots have no proven starter, but at least four rotational depth players in Logan Ryan, Malcolm Butler, Kyle Arrington, and Alfonzo Dennard (and it could be argued that Dennard is a back-end of the roster player).
Offensive Interior: There is no left guard and there is no quality rotational depth players to back-up Bryan Stork or Ryan Wendell.
Defensive Interior: New England has their starter in Sealver Siliga, as well as rotational players in Alan Branch, Dominique Easley, and Chris Jones. If the expectation is to move forward with Siliga and Easley as the starters, then the Patriots might not have an actual top need at this position, with Jones and Branch as the rotational depth.
The team needs potential starters at both guard and cornerback. They also need depth at guard, as well as defensive tackle, linebacker, and potentially wide receiver (depending on the perception of Aaron Dobson).
The question with the draft is asking how a team can best game the talent in order to maximize the value of their draft picks, or draft capital. A simple breakdown is by position, where there are clear premiums for, say, a quarterback versus a punter. Taking the best quarterback in the league in the 1st round is way better value than taking the best punter in the 1st.
Another method of positional comparison is by approximate value (AV). Pro Football Reference is a database site that uses historical information to generate a value for each position, based upon the individual and the team's success. This is the method we'll use to determine the best use of capital.
It's no leap to say that the earlier the draft pick, the greater the expected value of a player- ex: the #1 draft picks is supposed to be better than the #101 pick.
And while this stands as a whole, it's interesting to look at a position's expected value compared to others in the draft.
Above, we have the expected value (in blue) of an offensive interior lineman by draft position. It seems as if there's three clear tiers of prospects: Day One, Day Two, and Day Three, and players selected in each tier are fairly interchangeable.
What this means is that a player selected in the top 40 would have an expected value of an All Pro caliber player. Players selected 40th-90th have an expected value of a top tier starter. By the shape of the graph, interior offensive linemen selected from 90th through the end of the draft all have roughly the same expected value, that of a rotational depth player.
So if the Patriots are interested in an All Pro guard, they would likely have to use their first round pick to increase their odds. But if they would be fine with a top level guard, they could use their third round picks in the 90s to receive roughly the same expectation as if they took the player 50th overall.
And this is important when it comes to developing a team, because here's the expectation for defensive backs.
Defensive backs nearly perfectly align with the expected value of every position grouped together. However, if you want to select an expected All Pro at the position, you would need to use a top 20 pick, versus the top 40 pick needed for an interior lineman. If you want a top tier starter as the expectation, then a pick in the 20-50 range would be necessary.
In other terms, if a team is looking for a cornerback and guard to be of equal production on the field, by AV, then a cornerback at 32 would have roughly the same expected AV as an interior lineman selected 96th.
When it comes to approaching the draft, the best teams flush out their roster across the board. The difference between a first round cornerback and a third round cornerback is far greater than the difference of a first and third round interior lineman.
But perhaps nothing is more striking that the expected value graph for a defensive tackle.
What this implies is that the difference in value of a defensive tackle taken 20th versus 40th is greater than the difference of a defensive tackle taken 40th versus 250th overall. If a team misses out on the top couple of defensive tackles, then the expected value of a defensive tackle at 30th overall is roughly the same as one taken 150th.
So when the draft comes, know that even though the left guard position is the most glaring hole on the Patriots roster, it might not be addressed until the third round- and that will be okay. The Patriots will be crossing their fingers for one of the top defensive tackle prospects to fall into the 20s before making a move- and if not, then they'll move on to cornerbacks, and address the defensive line with a later pick.
Teams need to approach the draft with the expected value of a pick and the expected value of a position in mind. By waiting to take a guard, the Patriots will be maximizing the expected value of their draft.