I'm also listing two players who could make the major leagues, either of whom would become the tallest player in major league baseball history if they ever make it to the major leagues. I've listed both players at the end of the list.
Tallest players to ever play Major League Baseball
1. Jon Rauch - 6' 11"
Relief pitcher Jon Rauch was the tallest player in Major League Baseball history with a height of 6' 11". Rauch pitched in well over 550 games in his MLB career. He was last active in the major leagues in 2013. Rauch pitched for six teams in his 11 year career and made almost $16 million in salary.
Jon Rauch gained notoriety in 2012, when then New York Mets rookie teammate Matt Harvey challenged him to a fight because Rauch threw water on the then rookie phenom as he was napping. Rauch quickly backed down from Matt Harvey, and never bothered him again. The Mets released Rauch after the 2012 season.
2. Eric Hillman - between 6' 10" and 6' 11"
Eric Hillman pitched for the New York Mets from 1992 to 1994. Hillman is listed in various places as being either 6' 10" or 6' 11", so he must be between the two heights, making him the second tallest player in Major League Baseball history.
T-3. Randy Johnson - 6' 10"
There is no doubt about who the best tallest player in Major League Baseball history is. That distinction belongs to Randy Johnson, who won 303 games, while pitching to a 3.29 ERA in his great career.
Randy Johnson is 6' 10" tall, and he used his tall frame to record 4,875 strikeouts in his career. That is the second highest total in Major League Baseball history, trailing only Nolan Ryan's total of 5,714.
T-3. Chris Young - 6' 10"
Starting pitcher Chris Young is also 6' 10" tall. After not pitching in the majors in 2013, 35 year old Chris Young is having a renaissance season with the Seattle Matiners in 2014.
T-3. Andrew Cisco - 6' 10"
Reliever Andrew Cisco, who 6' 10" tall, pitched in the major leagues from 2005 to 2007, without much success. Cisco was as wild as a pitcher can be, as he walked 93 batters in 151 innings pitched. His career ERA was 5.18.
T-3. Andrew Brackman - 6' 10"
Andrew Brackman, who also stands 6' 10" tall, has pitched in three total games in the majors so far in his career, all for the New York Yankees in 2011. I'm a Yankees fan, and the team used to tout Brackman as a future star pitcher, but his career ERA in the minor leagues is 5.38.
Two players who would be tallest ever if they make the major leagues
- Frank Szczepanik - 7' 2"
Pitcher Frank Szczepanik, who stands 7' 2" tall, pitched in college for Division II Barry College in Florida. He would be the tallest Major League Baseball player ever if he makes it to the major leagues. He's was not a great college pitcher, though, so it's doubtful he will ever make it.
- Loek Van Mil - 7' 1"
Loek Van Mil, who is 30 years old and stands 7' 1" tall, has pitched in the minor leagues for eight years. Van Mil's career ERA in the minors is 3.23, so he might get a shot at pitching in the major leagues one day (Van Mil is pitching in Japan in 2014).
If he ever does make the big show, Loek Van Mil will become the tallest player in Major League Baseball history. I'm pretty sure that Loek Van Mil is the tallest player in minor league baseball history.