Front Office Football Central - Help on streamlining a query in MySQL

I'm trying to look at some era comparisons in FOF. I'm wanting to start with something basic: player ypa for a season versus league-wide ypa for the season. The idea here is that if a guy gets ypa above the league-wide average, he gets a score over 100. It it's below the league-wide average, his score is under 100. Here's the query I created (not certain if this *should* work, even...)

Code:

SELECT sum(s.passyards)/sum(s.passattempts) AS ypa, s.year,  lastname, firstname,

((sum(s.passyards)/sum(s.passattempts))/(SELECT sum(s1.passyards)/sum(s1.passattempts) FROM fof_playergamestats s1 where s1.year=s.year))*100 AS pct,

(SELECT sum(s1.passyards)/sum(s1.passattempts) FROM fof_playergamestats s1 where s1.year=s.year) AS leagueypa

FROM fof_playergamestats s

JOIN fof_playerhistorical h on h.id=s.playerid

GROUP BY s.playerid, s.year

HAVING sum(s.passattempts)>319

ORDER BY pct desc limit 50

It has been running for 10 minutes already, on a relatively fast server. That seems excessive, and I suspect that it's because of something I did wrong there in the nesting. Li'l help?