I think we’ve all heard that old idiom about leaving it all out there on the field, draining yourself completely so that no questions remain as to your effort. That doesn’t really work for starting pitchers though, as you can’t just go balls-out every time you take the bump and hope to have an arm left in the 4th inning, let alone the 4th month of the season.
Ah, but it’s a little different for a reliever. Given that they may only pitch an inning or so, maybe two on occasion, they can really rare back and sling it with a bit more abandon than their stretched-out brethren.