As listed in the collective bargaining agreement, Major League Baseball selects the field for its annual Home Run Derby according to nine factors, ranging from number of homers hit during the current season to the All-Star Game’s location to simple popularity. Not listed might have been the most important factor in creating this season’s field: willingness.

MLB announced the eight hitters for Monday night’s Home Run Derby at Nationals Park after 10:30 p.m. Wednesday, apt timing for the wattage of the players. Bryce Harper is the main attraction, a hometown slugger and worthy heir to past derby dignitaries. He’s joined by seven players who could politely be referred to as up-and-comers, or less charitably be called Freddie Freeman and some pretty good players who said yes when the league asked.

Along with Harper and Freeman, Max Muncy, Javier Baez, Alex Bregman, Kyle Schwarber, Rhys Hoskins and Jesus Aguilar will bash Monday night. There is appeal to all of them: Bregman is a World Series hero, Aguilar came out of nowhere to lead the National League in homers, Muncy is leading the Los Angeles Dodgers a year after getting released, Baez is one of the most electric players in the league, etc.

“It’s a cool group,” Hoskins said. “It really reflects how this game is going, right? There’s a lot of young talent in Major League Baseball. I think it’s cool the league has decided to showcase some of that.”

But the field is defined as much by who is not there. As the NBA has seen with its slam dunk contest over the past decade, MLB’s best power hitters are skipping the derby more and more.

In the mid-1990s, the Home Run Derby became one of baseball’s marquee events, as players such as Barry Bonds, Mark McGwire, Cal Ripken Jr. and Ken Griffey Jr. took part. The star power of the field has slowly decreased, but even last year, Giancarlo Stanton and Aaron Judge provided a jolt with every hack.

Stanton and Judge declined this season, as did Mike Trout, home run co-leader J.D. Martinez and most of the league’s greatest power hitters. Of the 18 players who have hit 20 homers this season (through Thursday’s games), only three will compete in the derby. Only half the entrants are actual all-stars this year, and only Harper has participated in the Home Run Derby before.

“You want the power guys – Joey Gallo, Aaron Judge, guys like that,” said Baltimore Orioles slugger Chris Davis, who competed in 2015. “I like to see guys hit balls 875 feet. It’s cool, man.”

The game’s best, most established players have opted against the derby for several reasons. Some believe it will alter or ruin their swings for the second half. Sometimes, coaches or managers insist players decide against it. Mostly, they would prefer as much rest as they can get in the middle of the marathon season.

Judge declined to defend his title because “there’s no need to do it,” he told the New York Post late last month. In the 60 games after he won the derby in Miami, Judge hit .195 with a .797 OPS. Judge played through an injured left shoulder late in the season, and this spring he said he would “rather not say” whether his derby effort contributed to the injury.

Trout has never competed, despite MLB’s several invitations. “I just never had any interest in doing it,” Trout told the Orange County Register. “It looks tiring.”

It’s telling that Harper is the only hitter who has participated before, and he committed, after skipping the previous four years, only because the game is in Washington and he made the All-Star Game itself. Many players are surprised by how fatiguing the derby is, especially in the new format, in which players try to hit as many homers as they can in a four-minute span.

“It’s extremely tiring,” Orioles slugger Mark Trumbo said. “It really taxes you, especially if you go more than one round. “I don’t think people realize how hard it is to swing more or less max effort for five straight minutes. For a couple weeks, I was a little bit sore. At the same time, it’s a heck of a lot of fun.

“There’s a lot of stress that goes along with being part of that event. It’s an honor for people that are selected, but don’t expect to get much of a recharge. You’re probably going to be pretty fatigued after it.”

The field of lesser lights may become the norm. Older players have little financial incentive for participating. MLB hands out $525,000 in bonuses, per the collective bargaining agreement: $50,000 for showing up, $25,000 for the longest home run, an extra $25,000 for the runner-up and an extra $75,000 for the winner. And veterans tend to regard rest as more valuable, while rising stars can bounce back more easily while receiving a jolt of recognition.

“Someone that’s a perennial all-star, I don’t think it’s as important for them,” Trumbo said. “For someone that’s maybe not a marquee name, it’s a cool experience. Those are the guys it makes a lot of sense for. It probably benefits younger players. I don’t think you’ll see quite as many 30-plus [players] participating.”

Some players fear the derby will spoil their swing, a notion that has produced massive debate within baseball for years. “The age-old question,” Davis said. In 2005, Bobby Abreu smashed the old record by hitting 24 homers in one round, then managed just six in the second half of the season. He insisted the derby had skewed his swing. Josh Hamilton broke Abreu’s record in 2008 – then never did the derby again, insisting he wanted to ensure his health.

“I think it’s a story that the baseball world tells itself,” Phillies Manager Gabe Kapler said. “As many cases as you can find on the side of a guy’s swing not being perfect after the Home Run Derby, you can find guys excelling.”

Most statistical studies have concluded hitting in the derby has little or no bearing on second-half performance. Analytical website declared the notion a “myth” in 2014, suggesting post-break decreases in production derived from simple regression to the mean. The league picks players for the derby because they had excellent first halves, frequently exceeding their typical output. The derby isn’t sinking them; they’re just reverting to their usual performance.

The derby is still a draw during a dead period on the sports calendar, especially after a new timed format reinvigorated the competition. Last year, 8.6 million viewers watched the derby, making it the second most-watched in the event’s history.

And it’s still a draw for many players, even as the biggest stars stay away. Davis said he would like another crack at the event.

Hoskins received a text message from one of his minor league host families Wednesday night, reminding him of the time they gathered around and watched the derby on television. Hoskins remembered watching old highlights of Bonds and McGwire going back and forth. Now kids will be watching him, for better or worse.

“It’s too cool of an opportunity to be a part of to say no to,” Hoskins said.

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