Who will win the Home Run Derby tonight? Here’s an answer you might not expect: It may be the guy who has the best batting-practice pitcher. There’s just no way to hit home run after home run without good pitches to hit.

It’s not easy throwing the same pitch in the same location at the same speed over and over again, but that’s what’s necessary to help a hitter win a home-run-hitting contest. Hitters have “happy zones” within the strike zone. Finding that spot and throwing a ball there over and over again is the job of the batting-practice pitchers who will throw to the derby contestants.

Watch what happens tonight when a hitter gets in a groove; he’ll hit a streak of home runs, one right after another, until something disrupts his rhythm. Say the hitter wants the pitch belt high and slightly inside. As long as the man behind the pitching screen can keep delivering the ball to that location, the hitter will stay in a good groove. Disrupt the hitter’s timing by throwing a pitch low and away, and the magic spell can be broken.

In 1999, Clint Hurdle — current Pittsburgh Pirates manager and then with the Colorado Rockies — traveled to Boston to throw BP to Home Run Derby contestant Larry Walker. Derby contestants often like to have the same guy on hand who throws to them every day. The BP pitcher should already know where his hitter wants the ball, and the hitter is familiar with the delivery of the BP pitcher.

But the familiarity of being on the Rockies together didn’t help Walker. As Hurdle says, “I was the only guy who could get Walker out that year.” Walker hit two home runs and was eliminated in the first round.

Hurdle, a former Royal, said the experience of throwing Home Run Derby BP was different. “Normally, you might have 112 people watching batting practice when you’re at home. When you’re on the road (after the ballpark gates open), it might be 5,000.” But throwing batting practice with 38,000 people hanging on every pitch changed things.

Hurdle said he stood in the same place, but there was no batting cage, and the derby uses a catcher, which isn’t done during regular BP. There were also crowds down each foul line. “It was like teeing off on a PGA fairway,” said Hurdle. Accidently leave a pitch inside, and a hitter might turn on it and pull into the people watching.

No wonder Hurdle threw his first pitch 43 feet. It bounced out in front of the plate, so Hurdle said he stepped back and mentally readjusted.

Despite Walker’s early exit, other hitters asked Hurdle whether he would throw to them as well. Before the contest was over, Hurdle had pitched to Walker, Jeff Bagwell, Jeromy Burnitz and eventual winner Ken Griffey Jr. It was estimated that before the evening was over, Hurdle threw 170 pitches.

So when you watch tonight’s contest, enjoy the hitters’ power and skill, but save a little appreciation for the guy pitching. He just might be the most important man on the field.