There're a lot of psychological states involved in special teams. Gunners need to have a certain craziness. Returners have to be loco enough to be ok with a guy ramming into them full speed with a 65 yard head of steam. When it comes to why teams plug in veteran guys to return at specific moments it has more to do with awareness and calmness than return ability. You don't want to be holding onto a 3 point lead late in the 4th, have your defense hold the other guys just out of their kicker's range, force them to punt, but stick a shaky wide-eyed rookie out there with the weight of the moment on his shoulders, and depend on him to have the awareness to judge the kick and in a split second determine where it's gonna bounce, how it's gonna fly, where he is, whether he should fair catch, or let it go into the end zone. That's why historically there were times where we'd stick an old and weary Ed Reed back there. You gotta have athletes back there, but also need to keep the older calmer guys ready to go.