From what I've heard others say who run fastbreak or press, it could have an impact if you're running either of those offenses or defenses, but since I've never run either of those sets, I can't really say. Otherwise, it's always better to have more speed, but, aside from any O/D-specific issues, you definitely shouldn't let a low speed prevent you from signing an otherwise good LP player at DIII, or DII for that matter.