Giannis Antetokounmpo continues to fill up the box score. But it's not translating to wins for the Miami Heat.

On the heels of three straight losses to start the season, the Heat held a 90-84 lead early in the fourth at home against the Dallas Mavericks Monday night. But Cooper Flagg took over down the stretch with 12 of his 29 points in the final stanza to lead the Mavericks to a 113-109 win.

Flagg added 11 assists, 5 steals and 3 blocks and looks just fine after missing a game with a shoulder strain.

Giannis triple-double, but no win

The loss for Miami spoiled another big effort from Antetokounmpo, who tallied 29 points, 14 rebounds and 11 assists for his first triple-double since joining Miami from the Milwaukee Bucks. It also dropped the Heat to 0-4, in a desperate search for the first win of the season.

Three of those losses have come at home, and the buzz of the Giannis era has quickly given way to anxiety in Miami.

What's wrong with the Heat?

The loss continues a trend for the Giannis Heat, who have gotten big efforts from the former MVP in each of his four starts. Antetokounmpo entered Monday averaging 28.3 points, 8 rebounds, 3 assists and 1.3 steals through his first three games.

But those games resulted in double-digit losses at home to the Timberwolves and Pistons and a 115-110 road loss to the Hornets on Saturday. The season-opening national TV showcase against the Wolves quickly turned into a 131-106 laugher in Minnesota's favor.

The shutdown defense that was expected from the frontline tandem of Antetokounmpo and Bam Adebayo has yet to materialize as the Heat have surrendered 113-plus points in each of their four games. And the Heat are struggling to find a reliable second option on offense behind a ball-dominant Antetokounmpo.

Davion Mitchell so far looks like it. He entered Monday averaging 17 points and posted 21 against the Mavericks. But it wasn't enough to secure the win.

The Heat are also struggling to control the boards and have lost the rebounding margin in each of their four games. With the Mavericks' 51-42 edge Monday night, the Heat have a 202-152 rebounding deficit through four games.

It's early, of course, but this surely isn't how the Heat envisioned the start of their new era after the high-profile offseason deal to acquire Antetokounmpo. Their next chances to get into the win column come on the road on Wednesday against the Hawks and at home on Friday against the Pacers.

From there, they'll embark on a five-game West Coast swing with games against the Lakers, Clippers, Warriors, Kings and Jazz. Starting a trip like that without a win does not sound like a good time.