We must have a different definition of what a run is...
To me, players in a run are basically interchangeable. It doesn't really matter who you get as long as you get one. For example, a typical closer run would be something like,
They are all the same to me, I really don't care which one I get as long as I get one.
No I agree with your definition, all of those closers are close to each other. I'd still rather have Nathan than Izzy though. Just because they are all closers you'd consider taking in the same round doesn't make them all exactly even in value. I like Lidge the best of the bunch, if I pick him and then next 6 of those all get picked in the next 7 or 8 picks its a big advantage for me because all 6 of those picks are guys that I had 0% chance of taking. If I take the 6th one then there are 0 picks ahead of me that I had 0% chance of taking. I'd much rather start the run than finish it.
An example is if I pick say 6th in the 4th round and Rivera has gone but no other closer. I will most likely take Lidge even though I'm not a fan of a closer in the 4th round, the reason being is the 7th-12th pick will most likely all be closers, its almost like taking a free pass on the rest of the 4th round as everyone that is going to pick after me is taking a player I had no intention of taking.
However the person with the 12th pick in the 4th is not only getting the weakest of the 6 closers most likely, the next 5 picks are almost for sure guys that he still had his eyes on since none of those players are going to take another closer which he doesn't need anymore.