On Thursday, the 2019 Major League Baseball regular season begins in earnest with the traditional Opening Day. The Athletics and Mariners already opened the regular season last week in Japan. The other 28 teams will start their seasons Thursday. Hooray for that.

Baseball is setting two age-related firsts this season. I'm guessing they're going to make you feel really old. First of all, welcome Blue Jays right-hander Elvis Luciano to the big leagues. He is the first player in MLB history born in the 2000s. Luciano turned only 19 last month.

Elvis Luciano
TOR • SP • #65
Date of BirthFeb. 15, 2000
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The Blue Jays selected Luciano from the Royals in December's Rule 5 Draft. As a Rule 5 Draft pick, Luciano must spend the entire 2019 season on Toronto's 25-man active roster, or be placed on waivers and offered back to Kansas City. If he does stick all year, Luciano will become the first player to play an entire MLB season (Opening Day through Game 162) as a teenager since Hall of Famer Ken Griffey Jr.

It should be noted Luciano was only available in the Rule 5 Draft due to a contract snafu. He originally signed with the Diamondbacks in July 2016, though they didn't like something they saw in his physical, so his contract was renegotiated later that fall. Arizona later traded Luciano to the Royals for Jon Jay, the Blue Jays took him in this past winter's Rule 5 Draft, and he is on their Opening Day roster.

When a player has his first pro contract renegotiated, he automatically becomes Rule 5 Draft eligible every year of his career. Usually players are not Rule 5 Draft eligible until their fourth or fifth professional year, when they are in their 20s. The renegotiated contract made Luciano Rule 5 Draft eligible as a teenager and allowed him to become the first MLB player born in the 2000s.

MLB: Toronto Blue Jays-Workouts
Elvis Luciano is the first 2000s kid in the big leagues. USATSI

In addition to baseball having its first player born in the 21st century, there are officially no more players remaining from the 1990s, which means there are no more players remaining from that century. With Adrian Beltre's retirement last year and Bartolo Colon's continued free agency, there is not a single player on an active roster who played in the 1900s. This is the first time that's happened since, well, the 1800s.

The longest tenured MLB player right now? Angels slugger Albert Pujols. He made his big league debut as a 21-year-old on April 2, 2001, with the Cardinals. Pujols beat current Yankees lefty CC Sabathia to the show by seven days. Sabathia debuted with the Indians as a 20-year-old on April 8, 2001. There are no other active players who debuted earlier than 2002.

The oldest active player is Athletics reliever Fernando Rodney. He is 42 years and 10 days old as of Opening Day, though he did not make his MLB debut with the Tigers until age 25 in 2002.