According to Pro Football Focus (PFF), David Garrard completed the second most "deep" pass attempts in the NFL in 2010 (completion percentage wise, bad wording). By their research, Garrard attempted 51 "deep" passes and completed 23 of them (45.10%). PFF defines a deep pass play as such:
We broke down every pass from the 2010 season, and dropped them into numerous categories and sub categories. One of these was passes thrown longer than 20 yards. Which brings us to the point of this article. A look at who threw downfield the most and who did it most efficiently. 30 deep attempts was the qualifying mark to be considered.
They don't really clarify, but I'm going to assume they mean passes thrown over 20 yards in the air and not just completions that netted more than 20 yards. According to NFL.com, Garrard had 39 passes go for 20+ yards, so that furthers my belief that is what they mean.
I'll say, that surprised the hell out of me. I didn't even think he'd register that many deep attempts, but then again I think a pass over 20 yards as "deep" is a bit of stretch. They don't provide the yardage for all the completions however, so we'll just take it for what it's worth right now.
Building on their deep pass research, while Garrard ranked 2nd in completions of deep passes, he also ranked 5th for most interceptions on deep passes and 14th in percentage of deep attempts, which is the amount of deep passes out of his total number of attempts (only 13.1% of his 366 total attempts). Looking at their chart, there were only 9 quarterbacks who attempted fewer deep passes than Garrard and only about 3 of those quarterbacks played at least an equal amount of games as Garrard (Sam Bradford, Chad Henne, and Brett Favre).
According to this, Garrard completes more "deep" passes than I intially thought, but I don't know if I'm inclined to call him a "good deep ball" passer, yet.