Yasiel Puig just had the best pre-game warm up of his life ... 'cause just a few hours before the Indians game against the Red Sox -- he got sworn in as a U.S. citizen!!!
The MLB superstar had the ceremony Wednesday ... and it didn't take long for him to pridefully post about it on social media.
"Thank you God for this great opportunity to be an American citizen," Puig said ... adding, "ususus."
Puig reportedly unsuccessfully tried to defect to America many times ... and when he did make it in summer 2012, the journey was long and treacherous.
He was taken by small boat to Mexico where he was held hostage by smugglers looking for a big money payout from the future MLB star.
Yasiel was ultimately taken to America ... and now 7 years later, he's a US citizen.
The Indians -- who are set for first pitch against Boston in Cleveland at 10 AM PT -- even shouted out the outfielder after the special moment, writing, "Puig our citizen"
"Congratulations to Yasiel Puig becoming a United States citizen!"
Of course, Indians players have done this often over the past year ... relief pitcher Oliver Perez was sworn in earlier this month, while infielders Carlos Santana and Hanley Ramirez had their ceremonies in April.