The Philadelphia Union faithful know this off-season is the off-season of the striker. The strikers of yesteryear are a mere ghost of themselves. Conor Casey might be back as a reserve and Pedro Ribeiro was lost in the expansion draft. Those two players accounted for nearly all the forward minutes under Jim Curtin. The roster up top is thin to say the least. The Union did not wait all that long to start the rebuilding process as they traded their first round SuperDraft pick to Sporting Kansas City for CJ Sapong.

Sapong is a young and talented forward that was the MLS Rookie of the Year in 2011. He topped that performance by scoring 11 goals in all competitions for Sporting Kansas City in 2012. In his last two seasons however, the emergence of Dom Dwyer has afforded CJ less playing time at his central forward position. Head coach Peter Vermes also pushed him out to a wide position at the top of Sporting KC's 4-3-3, and his numbers have not surprisingly declined.

Will the Union be the place to resurrect his promising career? Here's a look at what CJ does well, where he needs work and how he might fit into Jim Curtin's system.

The good news: CJ is a monster in the air

CJ Sapong's most outstanding capability is that he wins a lot of balls in the air. In fact, he led MLS is aerial duels won per 90 minutes by a pretty wide margin.

Union fans are used to watching Conor Casey battle for every ball in the air, and he did rank 7th in the league in winning header duels. But Sapong wins 39% more of them per 90 minutes than Casey. The Union led the league in crosses last season and next season they will have an outstanding threat for those balls that too infrequently found their target.

The meh news: CJ is an above average finisher with a disappearing left foot

What separates the elite strikers from the run-of-the-mill strikers is the ability to finish. In his first four seasons with Sporting KC, CJ has finished 12.4% of his shots taken and scored 20 goals. The league average ranges between 10% and 11%, so while Sapong has been above average, he has been far from elite.

The nerds over at American Soccer Analysis were kind enough to send me details of all of Sapong's career shots attempted, and there are some interesting findings. Check out what body part Sapong uses when shooting since he's been in the league.

He consistently uses his right foot about half the time, but over time he's used his head to shoot more and completely stopped using his left foot. This would make sense except that he has the best finishing rate when using his left foot.

This could be a function of where he takes left footed shots from. For example he may only use his left foot when he is very close to the goal, which would increase his likelihood of scoring. Except that's not the case. Throughout his career Sapong has shot furthest from the goal with his left foot. Yet he scores at better than twice the rate when he shoots with his favored right foot. Go figure.

The bad news: CJ Sapong is not a great passer

Sapong completed 60.7% of his passes last year, down from 65% the year prior. While that number is low for any player, it is always difficult to assess completion percentage without understanding what the role of the player is. CJ. played wide at the top of a 4-3-3, and so his passes would normally be looking to attack and his pass completion percentage would naturally be lower. So we need more context. Context comes in the form of Soony Saad and Sal Zizzo. Sapong split the wing role with Sal Zizzo and Soony Saad (and of course Graham Zusi, but he's in a different tier). The three headed winger of Zizzo, Saad and Sapong played roughly the equivalent of a full season's worth of minutes at the same position, on either the left or right side of the top of the 4-3-3. When comparing the high level passing statistics of the three players, Sapong's numbers are significantly worse.

Not only did Sapong struggle to score when placed out wide but he also struggled to create chances to score for his teammates. Just to put Sapong's .41 key passes per 90 minutes number in perspective, that number is lower than Ray Gaddis' number for 2014 of 0.5, who plays much further away from the goal. And Ray is not known for creating offense. Pause on that one for a minute.

Where does CJ Sapong fit in Curtin's system?

When Jim Curtin took over for Hackworth one of his tactical moves was to have his forward Conor Casey play as a holdup striker and come back consistently to get the ball. Here is a passing chart of Casey's from an August match against Montreal, when the Union were in peak form.

Most of Casey's passes are deep for a forward and from that position he is mostly looking to make short passes. By contrast, the majority of Sapong's passes where higher up the pitch.

This game was a particularly poor passing day for Sapong, as all five of his passes into the 18 yard box did not find their target. While Sapong was deep for a handful of passes, it's hard to image that he could play the deeper holdup role that Casey played for Curtin last year. Passing is only part of the job and I don't know how strong his holdup skills are, but his ability to distribute appears to be too much of a risk for Curtin to count on.

His ability with headers however would be something a coach would want to exploit within the 18 yard box, but that would put him higher up and require the midfield to bring the ball up themselves, rather than through a Casey type forward.

Sapong then, in my opinion, will provide Curtin with tactical flexibility and an ability to approach opponents differently than he could last season. Here are two ways I can see the use of Sapong benefiting the Union:

1. Jim Curtin has said that he is interested in bringing back Conor Casey in a reserve role, and that he is still looking to bring in a striker. Assuming the new striker is a legitimate threat, Curtin would have enough depth to use a two striker system, like a 4-4-2. In that formation one striker tends to play a deeper holding role and one plays the target up top. Sapong could be an ideal target man if Curtin chooses to go that route.

2. With Casey no longer the go-to option, Curtin may eschew using the striker as deep as he did. He may actually prefer a target striker like Sapong to be available to roam on counterattacks and using the midfield to setup the offense.

He also may choose to try both of these options in certain game situations, or simply to keep the opponent off balance. Much of this will depend on who the new striker is and what capabilities he brings.

With the Union still in striker acquisition mode, CJ Sapong looks like an acquisition that provides the Union with a talented player with upside, and one that gives Curtin flexibility in how to attack teams. He doesn't project to be the starter if Curtin stays with his 4-2-3-1 formation, but could be used as a dangerous change of pace off the bench.

While we wait for the next piece of the Union off-season puzzle to fall into place, please see if you can go find Sapong's left foot. It just might be the key to his revival.