Ronald Acuña Jr.'s All-Star Game Chain Worth $145k In Diamonds!

Ronald Acuña Jr.'s "too small" chain he rocked before the All-Star Game was anything but that ... and TMZ Sports has learned the flashy piece is worth a whopping $145k in diamonds!!

The Atlanta Braves star certainly turned heads prior to his fourth ASG appearance on Tuesday ... rocking an all-pink 'fit with an iced-out mini version of himself doing his famous celebration around his neck.

Gabriel the Jeweler -- go-to guy for some of the biggest names in sports -- tells us the piece is made of 80 carats total ... and the one-of-a-kind accessory was designed in collaboration with Xample Brand, Acuña's agency.

We're told Xample likes to treat Acuña to a new chain for every ASG appearance ... with each one documenting a new characteristic of Ronald's game.

Of course, Acuña's known to do the "too small" gesture whenever he hits homers ... so this year's jewelry was a no-brainer.

The chain itself is Gucci style and composed of brilliant diamonds and baguettes ... and we're told Ronald's family was also gifted smaller versions of the piece as well.

"I am blessed to be selected to play in this year's All-Star Game, and thank everyone who supported me on this journey and believed in me," Acuña Jr. tells us.