Al Horford's season is fairly straightforward to recap: He's a delight to watch on both ends of the floor, he's not a big enough part of the offense, and that fact combined with the time he missed due to injury might have obscured the encouraging and, one hopes, significant improvements he made in his second year in the league.
While essentially repeating his rookie production in terms of FT%, DR%, and S%, Horford improved his production in the following areas...
Scoring: 12.4 Pts/36 minutes, up from 11.6 Pts/36 minutes
FG%: 52.5%, up from 49.9%
FT Rate: 25.1, up from 23.2
A%: 11.9%, up from 7.9%
TO%: 13.1%, down from 15.3%
BS%: 3.3%, up from 2.2%
stats courtesy Basketball-Reference.com
I think the increase in scoring is most impressive as his usage rate didn't increase much: up from 16% to 16.4% and using 16.4% of the team's possessions puts Horford in line with Zaza Pachulia and Acie Law IV (both had 2008-09 usage rates of 16.3%). Yes, Al Horford is, relatively speaking, an equal part of the team's offense as his backup and the team's third string point guard. Unless he shared the court with Maurice Evans or, on very rare instances (138 minutes over the course of the season), Solomon Jones, Al Horford was clearly the Hawks' fifth offensive option.
Usage Rate, 2008-09 Atlanta Hawks
Al Horford didn't improve his numbers because his team made better or more frequent use* of him. Al Horford improved because he improved his skills and decision-making. I'm worried about the long-term production of Joe Johnson, Josh Smith, and (if they return) Mike Bibby and Flip Murray, but I'm confident that Al Horford gives the Hawks a fairly untapped offensive resource which could build upon his solid rebounding and defensive play to create an excellent NBA player. He's the closest thing to an untouchable player on the roster and the most likely member of the current roster to be on a Hawks team that reaches the Eastern Conference finals should that accomplishment ever come to pass.
*Were I sufficiently resourced and productive, I'd love to attempt to figure out how many of those possessions Horford did get to use came as a result of grabbing an offensive rebound or other manner of loose ball rather than as a result of a set play. There was more than one night that the Hawks' offense looked best for five-second stretches where Horford got the ball unexpectedly and hap, in that unscripted moment, the opportunity to use his skills either to get to the basket or find a wide open teammate. I suspect it's not a significant amount over the course of 82 games, not least of which because he got to significantly fewer offensive rebounds in his sophomore season (2008-09 OR%: 7.6%, 2007-08 OR%: 11.4%) but anecdotally it stokes one's desire to see Horford take on a greater offensive role both as a scorer and a passer.