I suggest he should not. My thesis: Fred Taylor's absence should have no impact on MJD's ranking.
First of all, the things that make MJD such an intriguing fantasy football player are not impacted by Fred Taylor. MJD gets a lot of red zone carries, hence his 34 rushing touchdowns in the past three seasons. MJD is a great receiver, hence his 148 catches and 1,408 receiving yards in the past three seasons. Fred Taylor did cut into MJD's rushing TD total in '06 and '07 (10 total), but only had one rushing TD in '08 (MJD had 12). And Taylor had just 48 receptions in the past three seasons, doing little to cut into MJD's reception total. Essentially, I think MJD's 2008 touchdown and reception totals are indicative of what we can expect from him in the future, with or without Fred Taylor.
Furthermore, MJD was already the dominant RB contributor for the 2008 Jacksonville Jaguars. In 2008, Jaguar RBs rushed for 1,445 yards, MJD netting 824 yards (57%). Perhaps percentage will improve without Fred Taylor, but I'm doubtful it will be significant. Jacksonville RBs had 15 rushing touchdowns, MJD getting 12 of them (80%). And finally, Jaguar RBs had 95 receptions, MJD getting 62 of them (65%).
Seriously, with or without Fred Taylor, how much more can we expect from MJD? He gets 57% of Jaguar RB's rushing yards, 80% of Jaguar RB's rushing touchdowns, and 65% of Jaguar RB receptions. Those percentages may go up without Fred Taylor, but I doubt they'll improve very much.
But one thing could improve MJD's rushing yardage: the success of the Jacksonville Jaguars. The '08 Jags went 5-11 and had 27 rushing attempts and 111 rushing yards per game. The '07 Jaguars went 11-5 and had 33 rushing attempts for 149 rushing yards per game. They did also decline from 4.6 yards per attempt to 4.2 yards per attempt, but for the most part, playing well and leading games means a team can rush the ball more. MJD could net more rushing yards--and more fantasy points--if the Jaguars are good.
Maurice Jones-Drew is an intriguing fantasy football player. In the past three seasons, he has averaged 84 yards from scrimmage per game and has netted 38 rushing/receiving touchdowns. I'm a little concerned about MJD's declining yards per attempt (5.7 in '06, 4.6 in '07, and 4.2 in '08), but I'm not sure that's predictive of his '09 numbers. But Fred Taylor's absence from the Jaguars doesn't really impact my view of MJD.
But as a fantasy footballer, you may need to know that Fred Taylor's absence will impact how other fantasy footballers view MJD. That means if you really want MJD, you will have to gauge the price accordingly.