and all the better for tennis, too
anyway, berdych is a factor?
chokes to murray, bends over for nadal, and gets trounced by djokovic
he plays against federer like its a calender year grand slam match, and mugs it up against everyone else
ferrer can at least beat murray on clay, nadal on hard and djokovic indoors
as i said, he's the best performer after the top 4, who else is more deserving as no 5?
Of course. He is a definite threat to Federer everywhere and to Djokovic on grass (not on hardcourts or clay) and has beaten them back to back in a Slam. Only Nadal truly owns him everywhere. Since you mentioned Murray, he has an even H2H to him and beat him at a Slam.
As for your question, Del Potro of course. He was actually #4 before he unfortunately had to leave the tour to get wrist surgery and very close to overtaking Djokovic for #3. His surgery/long layoff has meant that at the moment he cannot play at that level, the level of the current top 4, but he's still easily the fifth best player in the world.
he'd get a few more sets, though.
I guess he could get one or two more sets. If he was in Roddick's shoes ie playing prime Federer, he'd never have taken a single set (or one at most, I guess), Fed needs to play like a complete mug to lose a set to Ferrer - and even when he does, he often ends up winning the set anyway, see their last two WTF matches.