Coolbaugh, the former third baseman who played 17 Minor League seasons, signed a Minor League contract with Houston on July 9, 2003, and played the duration of that season with Double-A Round Rock, before playing all of 2004 and 2005 at the Triple-A level. He was the MVP of the then-Triple-A Round Rock team in 2005, hitting .281 with 27 home runs and 101 RBIs.
He also went to big league Spring Training with the Astros twice, and as recently as this spring, he interviewed for a coaching position within the Houston Minor League system.
Coolbaugh was a certain September callup for the Astros in 2005, and should've been part of the first championship team in Astros baseball history. But two weeks before his Minor League season ended, his wrist snapped after he was hit by a pitch and his season ended prematurely.
"I felt sick to my stomach," Astros general manager Tim Purpura said of his reaction to the news of Coolbaugh's death. "He was a great baseball guy and a great dad. He's somebody who loved the game and was the consummate professional.
"Thinking about it, the hard time for me is 2005. I remember sitting with Phil [Garner] when we sent him out of big-league camp. And he asked, 'Should I just forget about this? Should I give it up?'
"And I said, 'No, Coolie, you're a good player. You just need an opportunity.' So he went off to have a monster year, was MVP, but unfortunately had his hand broken. We were going to call him up in September. There was no doubt about it. I felt so bad for him."
Second baseman Chris Burke spent time with Coolbaugh in each of those three Minor League seasons, and he remembers him as someone much like himself.
"He was one of the first guys I played with that was a real veteran hitter," Burke said. "Our styles were very similar. We're both analytical. We spent hours talking about the game and at-bats and situations. I very much enjoyed my time playing with him, and I learned a lot from him. It's a shame, because he probably would've had a great career in coaching. It's a sad day.
"He and I both had fathers that were extremely passionate about the game, so we'd share stories all the time about our dads not talking to us after we didn't get a hit. Mike was like a self-admitted grump. It was kind of funny. He'd walk in and say, 'Don't talk to me today. I'm in a bad mood.' But he had such a big heart. Everybody knew he'd give you the shirt off his back. He cared a lot about the game and was a terrific player."
Reliever Chad Qualls spent time with Coolbaugh in 2003 and 2004, and credits him with the development of his two-seam fastball.
"He was just loved by the baseball community," Qualls said. "You see so many faces and names, but that part of your life, you remember. He helped me quite a bit when I was starting to throw my two-seamer. From a hitter's aspect, he'd tell me why it was such a good pitch and what I needed to improve."
Coolbaugh and Eric Bruntlett played together at Triple-A New Orleans in 2004, and Bruntlett recalls the third baseman taking on a leadership role.
"He was one of the guys who helped out with the younger guys a lot," Bruntlett said. "He had been around the game a long time.
"You don't think going to the ballpark that that's a possibility. "I've never heard of anything like that happening. It's a terrible tragedy."
But more than anything he did on the field, it's the impact of Coolbaugh's death on his family that weighs first on the minds of his former teammates.
"Everybody's just devastated," Burke said. "The family involved; his wife, Mandy, is a really sweet lady. They've got two boys and another child on the way, so it's just a really tough situation. I just keep putting myself in her shoes. You think your husband is going to a baseball game, and next thing you know someone calls you and tells you that he's dead.
"It's a tough deal, and it's one that I find myself asking myself a lot of questions about. I don't know if this has ever happened before in the history of the game, and the fact that it happened to Mike Coolbaugh is a pretty tough pill to swallow.
Luke Scott played with Coolbaugh in 2004 and 2005, and he fondly remembered the dedication Coolbaugh had to his family.
"He was a great teammate," Scott said. "An all-around good guy. I just remember he always had his kids around. He always took time to hang out with his family and play with his kids."
Reports indicate that Coolbaugh was struck in the temple of his head from a foul ball, immediately dropping to the ground and losing consciousness. He regained a faint pulse after he was given CPR on the field, but died before reaching the hospital.
"It shows you how fragile the temple is," Burke said. "I guess the ball blindsided him. For a ball to hit you right square in your temple from 90 feet away, it's almost too hard to believe.
"But obviously it's real, and there's a Coolbaugh family back in San Antonio that's very real too, and it's a very sad situation."
In Round Rock, where Coolbaugh played for parts of two years, a collection was taken 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 from each of the league's eight teams, will go toward the fund.
Ben DuBose is an associate reporter for MLB.com. This story was not subject to the approval of Major League Baseball or its clubs.