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The Buffalo Bills drafted EJ Manuel 16th overall to be the franchise quarterback. A review of his rookie season shows that while he possesses some of the necessary tools to succeed in the NFL, he must diversify his game if he's ever going to develop into a top-flight NFL quarterback.

Manuel's rookie season got off to a rough start, as the 2013 NFL draft's only first-round quarterback endured a knee injury that threatened to keep him out Week 1. His performance against the New England Patriots, in the first game of the season, turned out to be one of his best of the year. He followed it up with another impressive and thrilling performance against the Carolina Panthers.

From there, things got shaky. Manuel did not complete more than 60 percent of his throws and a 75 passer rating in a game again until November.

But it goes deeper than just the numbers. They all account for something that happened on the field. There's a lot to digest. In order to get a feel for Manuel as a passer—what he does well, and what he struggles to do well—it only seemed fitting to go back through each of his dropbacks from 2013 to see what happened.

Here is a chart I've compiled of all of Manuel's throws from last season. What follows here are the numbers I've chosen to crunch and some thoughts on the observations.

Route

A lot of times, when you hear analysts talk about quarterbacks, they'll ask the question: "Can he make all the throws?"

The only way to find out was to chart each throw, based on the route run by Manuel's intended target. The numbers show some interesting conclusions.

EJ Manuel throws, by route (aimed passes only) Route Comp Att Comp % Yds YPA TD INT Drop Rate Checkdown 14 21 66.6 85 4 0 0 1 74.5 Circle 5 5 100 51 10.2 0 0 0 109.2 Comeback 3 9 33.3 42 4.7 0 0 0 49.3 Corner 4 8 50 51 6.3 1 0 1 109.4 Cross 2 3 66.6 22 7.3 0 0 0 88.2 Drag 7 10 70 71 7.1 0 0 0 90 Fade 3 14 21.4 81 5.8 1 0 0 75 Flare 15 22 68.2 82 3.7 1 0 1 89.6 Freelance (scramble) 0 1 0 0 0 0 0 0 39.6 Go 4 11 36.4 127 9.4 3 0 0 120.1 Hitch 16 25 64 175 7 1 0 0 97.9 In 11 22 50 190 8.6 0 2 2 41.9 Out 16 25 64 131 5.24 0 0 2 77.3 Out-and-up 0 3 0 0 0 0 0 0 39.6 Pivot 4 7 57.1 23 3.3 0 0 2 63.4 Post 4 5 80 101 20.2 0 0 1 118.8 Screen 13 16 81.3 74 4.6 1 1 1 80.7 Seam 4 8 50 93 11.6 1 0 0 131.8 Skinny post 3 5 60 90 18 1 1 0 104.2 Slant 13 24 54.2 186 7.8 0 3 4 39.9 Slant-to-post 0 1 0 0 0 0 0 0 39.6 Stick 19 24 79.2 155 6.5 1 1 2 90.1 Swing 19 22 86.4 117 5.3 0 0 0 88.8 Wheel 1 4 25 17 4.3 0 0 0 44.8 Source: Bleacher Report research

A combined 134 of Manuel's throws were to a receiver running either a flare route, a hitch, a screen pass, a slant, a stick route or a swing pass. Many of those were one-read plays.

Manuel's numbers look awful on comeback routes, but his receivers were routinely running sloppy routes and slipping on the ground out of their breaks. That's part of the end result when the investment has routinely been in speedy receivers with questionable route-running ability. If Mike Williams can run a comeback, he will be well worth the investment of a sixth-round pick.

The other route that stands out is the fade.

It's a low-percentage throw, especially down the sideline, which is where most of Manuel's fades were aimed. There's a very small spot between the defender, receiver and sideline that the quarterback must fit the pass in order for it to be caught.

Source: NFL Game Rewind

Manuel did that to perfection against the Jets in Week 11 on a deep throw to T.J. Graham down the left sideline. The throw traveled 40 yards through the air before it dropped in the bucket, landing directly in Graham's hands, extended to make the over-the-shoulder catch.

That was a culmination of a season's worth of work. It was the fourth time Manuel had tried to hit Graham on a fade and only the first that had been completed. For the record, he attempted five fades to Robert Woods (one completion), four to Stevie Johnson (one completion) and another to Marquise Goodwin (incomplete).

Part of the problem may be asking receivers like 5'11", 188-pound Graham to run a route that requires him to win a physical matchup on the sideline. Perhaps bigger, more physical receivers like Mike Williams and Sammy Watkins can help the cause. Manuel still has to improve; he didn't give his receivers much of a chance to catch the fade routes that were incomplete.

Distance

EJ Manuel throws, by distance traveled Yards downfield Comp Att Comp % Yds YPA TD INT Drop Rate Behind LOS 27 34 79.4 125 3.7 1 1 2 79.5 0-9 112 167 67.1 961 5.8 4 4 14 80 10-19 30 57 52.6 550 9.6 3 2 2 89.1 20+ 10 37 27 323 8.7 3 2 1 68 Source: Bleacher Report research

The high concentration of throws within 10 yards of the line of scrimmage gives them no recourse when defenses crowd the box.

It may sound backwards, but Manuel needs to hit more deep throws if the Bills' offense is going to continue on its rhythm passing ways. It's the only way defenses will open up the short area of the field.

The ability to hit those deep throws has been the burning question for Manuel. He was hailed for his big arm coming out of Florida State, but as of yet, he has failed to translate the talent to production at the NFL level.

One thing jumped out when re-watching all of his deep pass attempts. His mechanics always looked as if he was working in a compressed pocket, whether he was actually under duress or not. The tight mechanics led to throws that were often off-target, one way or another.

Some were overthrown, sailing harmlessly over everyone's head.

Source: NFL Game Rewind

Some were underthrown, in danger of being intercepted.

Source: NFL Game Rewind

All shared one trait: A lack of follow-through in the throwing motion. He doesn't rotate his hips cleanly, and he short-steps his back foot where he should be following through with it a little further. It looks like he is operating in tight quarters, even when there is plenty of space around him.

Both of those throws were from early in the season, though. There were signs of progress as the season wore on.

Source: NFL Game Rewind

With 12:23 to go in the fourth quarter against the Atlanta Falcons, Manuel hit Woods on a go route that gained 33 yards. His hips turn into the throw and his back foot follows through.

The receiver was wide open and unaccounted for down the sideline, but Manuel still had to fit the throw into a tight spot. The ball traveled 30 yards through the air before landing perfectly in Woods' waiting arms, where he secured it before taking a vicious (and illegal) hit after the fact.

With mechanics (and clean pockets) like this, Manuel should be able to hit plenty of these throws in the future, but only if his footwork becomes more consistent.

Progressions and Play Calls

There is no way to measure progressions. You can see which direction a quarterback's head is facing, but it's impossible to tell where his eyes are focused.

It's not hard to see, though, that most of the plays were designed to go to the first read.

Source: NFL Game Rewind

Take this play against the Jets, for example. Marquise Goodwin (circled in black) runs a seven-yard hitch route. Manuel's head is clearly turned that direction the entire time, as he waits for Goodwin to hit the top of the route before releasing the ball. Because of Goodwin's speed, rookie cornerback Dee Milliner began backpedaling early to prevent being beaten over the top.

Go to the well too many times, though, and you're bound to run out of water eventually.

Source: NFL Game Rewind

Later in that same game, Manuel threw another hitch route to Goodwin on his first read, never taking his eye off the receiver. Where the rookie corner was fooled, veteran cornerback Antonio Cromartie smelled blood and nearly seized the opportunity. Cromartie broke on the ball, nearly intercepting the pass.

One recurring theme over the course of the season was Manuel's lack of field awareness. Most of the route combinations were very simple. On plays that were not designed to go to the first read (of which there were many), if the first read was not open, Manuel frequently checked down to the running back.

Many times, it turned out to be a smart decision. Sometimes, however, there was room to wonder if a receiver downfield might have been a better option.

EJ Manuel throws, by alignment (not including penalties) QB alignment Comp Att Comp % Yds YPA TD INT Drop Rate Shotgun 146 237 61.6 1504 6.3 8 8 18 77.1 Under center 34 67 50.7 442 6.6 3 1 3 80.6 Source: Bleacher Report research

The Bills could help Manuel out by mixing up the play calls and having EJ line up under center more often. By my calculations, only 85 of Manuel's 358 drop-backs (23.7 percent) were from under center. The rest were out of the shotgun.

Manuel's footwork may be an issue, but it will never get any better if he doesn't practice it in games.

If the Bills give Manuel more opportunities to go through his progressions, and if Manuel begins hanging in the pocket long enough to see his receivers downfield, they could expand the offense and open up the play calls.

With a new bevy of weapons at his disposal, Manuel could find life in the pocket a bit friendlier this year than last.

Erik Frenz is also a Patriots correspondent for Boston.com.

Follow @ErikFrenz