Coolbaugh, 35, was hit by a line-drive foul ball in the ninth inning of Sunday's game and never regained consciousness. Several athletic trainers for both teams worked to keep Coolbaugh breathing on the field, but he died en route to the Baptist Health Medical Center in North Little Rock, Ark.
The San Antonio native leaves behind two sons, Joseph, 5, and Jacob, 3, and his wife, Amanda, who is expecting their third child in October. A collection will be taken up for the Coolbaugh family at the home plate and right field gate entrances of The Dell Diamond prior to Monday night's game between Round Rock and Oklahoma.
All donations collected will go directly to a fund set up for the family at Spirit Bank in Tulsa, Okla. In addition, all fine money from the Texas League, plus an additional $1,000 for each of the league's eight teams, will go toward the fund.
"It's an extremely sad tragedy," said Round Rock Express founder and C.E.O. Reid Ryan. "Mike was a veteran around baseball and befriended a lot of us. He spent two years here and made an impact on our fans and the entire Express family."
Coolbaugh attended Roosevelt High School in San Antonio and was drafted by the Toronto Blue Jays in the 16th round of the 1990 draft as a 19-year-old. Over his 16-year career, he was involved in 25 transactions and played for 17 professional teams.
He broke into the Majors after a decade in the Minor Leagues, collecting 14 hits in 39 games with the 2001 Milwaukee Brewers. Coolbaugh, a true third baseman, appeared in five games with the St. Louis Cardinals the following season before joining the Houston Astros' farm system in 2003.
Coolbaugh hit .259 with the Double-A Round Rock Express in 2003 and had a career year in 2004, batting .295 with 30 home runs for Triple-A New Orleans.
"He was a tremendously hard worker who met a lot of adversity in his career and found a way to keep moving," said Express president Jay Miller. "He was a standout guy both on and off the field."
In 2005, Coolbaugh was voted to the Triple-A All-Star game and was named the Houston Astros' Triple-A Most Valuable Player after batting .281 with 27 home runs, 30 doubles and 101 RBIs. He also moved his family back to San Antonio that year to be closer to his brother, Scott Coolbaugh, who spent parts of his 11-year career as the third baseman for the Texas Rangers.
Mike Coolbaugh played for Tulsa in 1996 and had been with the team for three weeks before Sunday's tragedy.
"He will be greatly missed," said Round Rock Express manager Jackie Moore. "It was a privilege to have had him on our teams ... a privilege to have known him both as a player and as a person."