"I'll never leave the team and the city of Milwaukee till we build the team to a championship level ...," he wrote.
It was the summer of 2014, and Antetokounmpo was a gangly, doe-eyed 19-year-old who spent the year videotaping himself drinking smoothies for the first time and building muscle. He had finished seventh in Rookie of the Year voting.
Fast forward five years: Antetokounmpo has blossomed into a physically imposing player and MVP favorite who led his team to the best record in the NBA.
The Bucks had lived a charmed existence most of the 2018-19 season. They waltzed out to 60 wins, secured the 1-seed and bulldozed the Detroit Pistons in the first round of the playoffs.
Milwaukee's first real trial was supposed to come against the Boston Celtics in the semifinals. Instead, the Bucks -- after dropping Game 1 -- rattled off four consecutive wins to advance to the Eastern Conference finals for the first time since 2001.
Then came the Raptors.
After jumping out to a 2-0 series lead in the conference finals, the Bucks crumbled. Milwaukee lost four consecutive games and fell in six.
In what would be their final game of the season Saturday, the Bucks led most of the game before unraveling late in the third quarter. The Raptors tied the game on a Serge Ibaka dunk with 10 minutes, 31 seconds left in the fourth quarter while Antetokounmpo was on the bench.
Brook Lopez hit two free throws with 29.6 seconds remaining to make it 97-94, but the Raptors finished it out at the free throw line to pull out a 100-94 victory and advance to their first NBA Finals, against the Golden State Warriors.
Now, Bucks co-owner Marc Lasry and general manager Jon Horst are headed into an extraordinarily busy summer. The contracts of three starters -- Khris Middleton, Lopez and Malcolm Brogdon -- need to be addressed. And they'll have to decide on the futures of George Hill and Nikola Mirotic, two key bench players, as they attempt to construct an even better team around their superstar.
This week, Antetokounmpo qualified for a five-year, $247.3 million supermax extension, the largest in NBA history, by earning All-NBA honors for the second consecutive season. He can't accept that agreement until next summer, once he has seven years of NBA experience, a timeline that clearly puts Milwaukee on the clock this summer.
Antetokounmpo has consistently made public proclamations of his love for Milwaukee, as he grew up and became acclimated to American culture in Cream City after moving from Greece. Antetokounmpo adores the Bucks medical staff. His mother moved to Milwaukee. But he is all about winning. In more concrete terms, a source close to Antetokounmpo said that getting to the NBA Finals is not just an ambition, it could tip the scales as he weighs his contractual future.
And if they can reach the NBA Finals next season, the Bucks can improve their chances of signing Antetokounmpo to the supermax in the summer of 2020.
This season, the Bucks were built to win.
Horst hired ex-Hawks head coach Mike Budenholzer on May 17, 2018. Horst upgraded the center position by replacing Thon Maker and John Henson with Lopez, a 3-point shooting 7-footer who could space the floor. He also signed Pat Connaughton, another shooter who could add depth to the Bucks' bench.
At the Bucks coaches' summer retreat, Budenholzer laid out his vision for the season: Do everything to accentuate Antetokounmpo's strengths. Nix Middleton's long 2s in favor of 3s. Instruct Eric Bledsoe and Brogdon to shoot more 3s. Maintain spacing on the perimeter to allow for Antetokounmpo's dominance in the paint.
"We really drilled that stuff," Lopez told ESPN in April. "Our offense is predicated on shooting."
Horst also traded for Hill and Mirotic -- shooters with playoff experience.
The Bucks finished the regular season No. 1 in defensive rating and No. 4 in offensive rating. They attempted and made the second-most 3-pointers per game in the league, and Antetokounmpo led the league in dunks.
The Bucks didn't lose back-to-back games until March 2 and 4. They lost a close game to the Jazz in Utah, then dropped a game on the road to the Phoenix Suns. The locker room was glum after both losses, but Antetokounmpo vowed that his team would be better.
Determined not to lose three games in a row, the Bucks bounced back against the Pacers in Indianapolis on March 7.
Antetokounmpo was issued a technical foul early on for being uncharacteristically vocal with the referees. Antetokounmpo credited his teammates with keeping control of the game when he lost his cool.
"That's the guys you want to play with," Antetokounmpo said. "They know their role, and they try to do the best job they can every single night. You could feel it, we didn't want to lose a third game in a row."
But which teammates will continue with Antetokounmpo in the Bucks' quest for a Finals appearance who could affect whether they keep their superstar when he's eligible for free agency in 2021?
The Bucks likely will pay Middleton. After signing Bledsoe to a four-year, $70 million contract in March, retaining Brogdon would come with a hefty price that could send the Bucks into the luxury tax. Milwaukee also will need to choose among Mirotic, Hill and Lopez. It is unlikely that all three will be retained.
Re-signing Lopez, league sources said, is a priority.
Game 5 of the Eastern Conference finals was the team's first real test of the playoffs. The series was tied. The Bucks were back on their home court. It was a crucial game.
After the Bucks squandered a 12-point lead with 7:43 left in the third, it came down to the final two minutes.
Trailing by three with 1:12 to go in the game, Antetokounmpo rolled his ankle and Budenholzer pulled him from the game. Rather than take a seat on the bench, Antetokounmpo leaned up against the scorer's table and watched as Kawhi Leonard went to the line and split two free throws.
This would have been a logical time for Budenholzer to call a timeout and reinsert his franchise player. Instead, the game went on without Antetokounmpo.
When Antetokounmpo checked back in, the Bucks trailed 100-97 with 34.7 seconds left, and it wouldn't get any closer.
A deflated Antetokounmpo exited the court with a towel draped over his head. He sat in front of his locker munching on a postgame snack. Twenty minutes later, he explained that he was "pissed" and "frustrated" but vowed this wouldn't be the end for the Bucks.
"We're the best team in the league," Antetokounmpo said. "We are not going to fold."
The Bucks might have been the best team in the league during the regular season, but the Raptors were right behind them and ultimately proved to be superior in the postseason.
Milwaukee made major strides this season and still has time to reach a Finals with Antetokounmpo. Even so, given Antetokounmpo's intense desire to win and his looming contract decision, the expectations and pressure are bound to increase next season.