You're lucky if you can read a recap of a Derby prep anymore without reading about the "come-home time" or closing fractions.
Emphasising closing ability is a GREAT way to go broke fast in regards to betting dirt racing. It can be an important factor in handicapping turf racing however.
Last years winner Super Saver had blown very easy early leads on multiple occasions:
He was unable to hold off Oddsyess and Schoolyard Dreams in the Tampa Derby. In the Arkansas Derby - he pressed a very fast paced set by sprinter Line of David. Super Saver collered him turning for home - but was unable to pass the entire length of the stretch.
2009 Derby winner Mine That Bird was the leader at the 1/4 pole in his prior two races at Sunland Park - he was unable to hold-on both times. He actually faded to 4th in the Sunland Derby - which was a very fast paced race early - and a brutally slow paced race late.
He wins the Kentucky Derby from a mile back because the change in tactics allows for his speed to be rationed efficently.
2008 Kentucky Derby winner Big Brown had a slower come-home time than the laughing stock Tomcito in his final prep - the Florida Derby. Big Brown was ultimately lucky to draw the 12 hole in the Florida Derby ... because it forced his jockey to gun him hard out of the gate.
He ran a 22 3/5 first quarter despite racing about 3-to-4 wide through the first turn. No trainer wants to see his horse absolutely sprinting early on - in his final Ky Derby prep. However, history shows it sets a horse up better for dealing with the Ky Derby pace.
Horses who exit a series of slow paced races often get baked by the Kentucky Derby pace. There are VERY few Derby preps each year that are truly fast paced races - but horses who ran in them... and either came home very slowly in victory .. or faded in defeat ... they have performed absolutely incredible in the Derby.