- Bats Left, Throws Right
- Height 6' 2", Weight 215 lb.
- School University of Miami
- High School Coral Gables High School
- Debut September 1, 2010
Born in Havana, Alonso left Cuba for the USA when he was 9 years old. He hit .405 as a high school freshman and .510 as a sophomore at Coral Gables High School in the Miami, FL metropolitan area. As a junior, he batted .420, followed by a .530 senior campaign, winning him All-State honors. He set single-season school records for average (.530), walks (33) and RBI (33) at the high school attended by Mike Lowell. He was a 15th-round pick in the 2005 amateur draft by the Minnesota Twins but opted for college.
The first baseman hit .295/.373/.492 as a freshman at the University of Miami and became the second freshman in school history to lead the team in home runs (10) and RBI (69); Ryan Braun had done so previously. He hit .273 in the 2006 College World Series. He hit 8 home runs in the Virginia Valley League.
Alonso batted .376/.519/.705 as a sophomore. He was second in the Atlantic Coast Conference in slugging and OBP, trailing Tony Thomas Jr.. He led the ACC in homers, tied with Allan Dykstra with 18. Alonso led the ACC with 64 walks and tied Dustin Ackley for the RBI lead, 74. He failed to make the All-Conference team due to the presence of Ackley at first base. Baseball America named him as a second-team All-American behind Brett Wallace.
Alonso had an excellent summer for the Brewster Whitecaps of the Cape Cod League, hitting .338/.468/.497 and leading the league in OBP. He was third in average, .007 behind Conor Gillaspie. He tied for second in hits (51) and tied Reese Havens and Gillaspie for second in doubles (12). He was named the All-Star 1B. Baseball America rated him the #2 prospect in the Cape Cod League.
Alonso hit .367/.535/.774 with 24 homers, 73 runs, 71 RBI and 74 walks to 23 strikeouts as a college senior. Yonder was 5th in NCAA Division I in OBP, 9th in slugging, 6th in homers and first in walks (12 more than anyone else). He was two home runs behind ACC leader Buster Posey. He was named All-Conference at first base. Baseball America and Collegiate Baseball named him All-American at DH while the American Baseball Coaches Association chose Ben Carlson; Justin Smoak was the consensus pick at first.
The Cincinnati Reds chose the Cuban slugger 7th overall in the 2008 amateur draft. He was the third college batter chosen after Pedro Alvarez and Posey. He was signed by scout Tony Arias for a $2,000,000 bonus. Alonso made his pro debut with the Sarasota Reds on August 26, 2008, going 1 for 3 with a double, walk and run against the Clearwater Threshers. He hit .316/.440/.368 in his six late-season games for the team.
Baseball America rated him baseball's 35th-best prospect going into 2009. In 2009, Alonso hit .292/.374/.464 with 9 homers and 41 walks in 84 games between the GCL Reds, Sarasota Reds and Carolina Mudcats, missing time with a hand fracture. Baseball America rated him as the #4 prospect in the Florida State League after Mike Stanton, Jesus Montero and Domonic Brown and just ahead of Kyle Drabek and Starlin Castro.
In the 2010 Futures Game, Alonso hit third and played first base in the World lineup, preceding Alex Liddi and Carlos Peguero in the heart of the order. In a 9-1 defeat, he was 1 for 4 at the plate. He struck out against Jeremy Hellickson in the first, flew out versus Zachary Britton in the third and grounded out against Jordan Lyles in the 6th before singling off Anthony Slama in the 8th.
In the minors that summer, the former Hurricanes star hit .267/.388/.406 in 31 games for Carolina and .296/.355/.470 in 101 for the Louisville Bats. He banged out 36 doubles and 15 home runs while his walk rate fell (just 56 free passes). He got a September call-up to the Reds.
He made his major league debut on September 1, 2010, making an out in a pinch-hitting appearance against the Milwaukee Brewers. Stepping in for Brandon Phillips, he grounded out against Zach Braddock. Three days later, the former first-rounder pinch-hit for fellow heralded Cuban defector Aroldis Chapman in his second MLB at-bat and connected for a bounce double off Mike MacDougal. He later scored on a hit by Joey Votto, the player blocking his path at first base. He hit .207/.207/.276 in 22 games in his first season, but went back to AAA in 2011 with Votto blocking his path. He hit .296 with 24 doubles and 11 homers in 91 games with Louisville, then was promoted back to Cincinnati. He played mostly in left field, making 14 starts at the position in 47 games, and hit a solid .333/.398/.545, including 5 homers. However, it was clear that left field was not a long term solution to get the young slugger playing time, and on December 17th, the Reds decided to use him in a trade, packaging him alongside Yasmani Grandal, Brad Boxberger and Edinson Volquez to obtain starting pitcher Mat Latos from the San Diego Padres.
He spent the 2012 season as the Padres' starting first baseman. He played 155 games and hit .273 with 39 doubles, although he only produced 9 homers playing his home games in pitcher-friendly Petco Park. His 62 RBI were second on the team, behind Chase Headley, but 14 more than the next best run producer. His OPS+ was 109, reflecting the difficult hitting environment in which he played. In 2013, he was set to become the brother-in-law of Manny Machado, as his sister Yannie became engaged to the Baltimore Orioles' third baseman. While he hit for a good .281 average, his power seemed to vanish completely, as he was limited to a paltry 11 doubles and 6 homers in 97 games. He managed to maintain an OPS+ of 104, because of Petco Park being such a hitters' graveyard that year, but his failure to connect for more extra-base hits was a big disappointment. In 2014, his average fell to .240 in 84 games, although his 19 doubles, 1 triple and 7 homers beat all three numbers from the previous year in many fewer at bats. The low batting average coupled with a precipitous drop in walks meant his OPS+ was down to 95 in spite of the increased power. Worst for him, his season ended early, as a torn tendon in his wrist put him definitely on the shelf in mid-August and made his future with the team uncertain. In 2015, injuries affected him again, limiting him to 103 games during which he hit .282 with 18 doubles, 5 homers and 31 RBIs. His OPS+ was back up to 111 as his numbers were again deflated by the limited playing time and his tough home park. On December 2nd, he moved to a more hitter-friendly environment as the Padres traded him to the Oakland Athletics, along with P Marc Rzepczynski in return for P Drew Pomeranz, minor league P Jose Torres and a player to be named (Jabari Blash).