Greg Swindell -- a former MLB pitcher who helped the Diamondbacks win the 2001 World Series -- is pleading for the public's help ... after he says his daughter has gone missing.
The 59-year-old wrote in a Facebook post over the weekend that Brenna Swindell, a single mom of three, went missing from the Austin, Texas area last Thursday -- and he and his family are worried sick about her.
Greg says her phone's been turned off and she has not been in contact with any one of her Swindell relatives -- including her own children.
The one-time All-Star did say in an update on Sunday that they believe Brenna is with her ex-boyfriend somewhere in Colorado ... but he added, "we feel she is in danger."
Greg says Brenna is about 5-foot-5, 120 pounds and has some notable tattoos on her arms, including ones of flowers and a spider web. He also suspected she and her ex might be driving around in her white Kia Carnival with the license plate VFS7528.
"Brennie," he wrote in his initial message to the public addressing the matter, "if you see this, we all love you so much and need you home!"
Greg -- the No. 2 overall pick in the 1986 MLB draft -- made his Big League debut just weeks after Cleveland selected him ... and he went on to throw in The Show for 17 seasons.
He logged a 3.86 ERA in his career, pitching for several teams -- including the Guards, Reds, Astros, Twins, Red Sox and D-Backs.