1 of a kind set. Alonso made the Mets Opening Day.
Roster in 2019 as the starting first baseman. Alonso was in the team's starting lineup on Opening Day on March 28, 2019, and recorded his first major league hit against Washington Nationals.
He hit his first major league home run on April 1 off of Drew Steckenrider. In the fourth game of his MLB career. On April 9, Alonso had his first career multi-home run game against the Minnesota Twins. Alonso became the first player in MLB history (since 1900) to have at least 11 extra-base hits in his first 10 career games. No other player ever had more than nine. 292 with nine home runs. 8 doubles, 1 triple and 26 RBIs in his first games in the big leagues. He won the National League Rookie of the Month Award. Alonso's nine home runs lead all MLB rookies and are tied for the most by a Mets player before May 1 with Neil Walker. On June 22, Alonso hit his 26th home run, breaking the National League record for most home runs by a rookie before the All-Star break, passing Cody Bellinger. Who set the record with 25 home runs in 2017. The next day, with his 27th home run, he broke the Mets rookie home run record, previously set by Darryl Strawberry. Alonso was selected as a reserve to the 2019 All-Star Game. He also won his second National League Rookie of the Month Award for the month of June. On July 7, Alonso became the second player in Mets history to hit the most home runs (30) before the All-Star break, tying Dave Kingman. On July 8, Alonso won the 2019 MLB Home Run Derby. Third baseman Vladimir Guerrero Jr. 23-22 in the final round, becoming only the second rookie after Aaron Judge.Won in 2017 to win the Derby outright. On the way to the final round, Alonso also beat Carlos Santana. Hitting 57 total home runs during the entire Derby.
On August 15, Alonso, in a 10-8 win over the Atlanta Braves. Hit his 39th home run, tying Cody Bellinger. For the most home runs by a rookie in National League history. Alonso finished the game with a career-high five hits and six RBI's. He broke Bellinger's record on August 18 with his 40th home run in an 11-5 win against the Kansas City Royals.
Alonso is the first Mets player to hit 40 home runs in a season since Carlos Beltrán. Hit 41 in 2006, as well as the fourth Mets player in total. On August 24, he tied the Mets' single-season home run record with his 41st home run, tying the mark set by Beltrán and Todd Hundley.
Three days later, on August 27, Alonso smashed his 42nd home run against the Chicago Cubs. Becoming the Mets all-time single-season home run leader. He is the first rookie to set his franchise's single-season home run record since Johnny Rizzo. Did it for the Pittsburgh Pirates.