Isbell posted a video on Twitter of Leonard working to fix the car, which has been viewed more than 676,000 times on Twitter.
The flat tire appeared to be another burden for Isbell, who has been taking care of her father, who is fighting stage 4 cancer, WXIN reported. But her former student bailed her out.
“The doughnut will have to do for now, but I'm OK,” Isbell told the television station. “I’m glad Darius was there to do it because my dad was about to try to come instead. He really was a blessing.”
Leonard and Isbell had a contentious relationship when the second-year Colts player was a high school student, the teacher said.
"Darius was finding himself at that time, so I was tough on him," Isbell told the Star. "He was the student that was kind of the class clown. He played a little bit. He had some friends and they wanted to make biology interesting. We had our differences."
Those differences had melted away as Leonard matured, and he was more than accommodating to his former teacher.
On the video, Isbell can be heard thanking Leonard, who said, "Hey, no problem."
"Thank the Lord for angels," Isbell says on the video.
Leonard quickly changed the tire, and Isbell made it to the church on time.
"He knew it was me," Isbell told the Star. "If I had been a complete stranger, he still would have done it anyway. He cares enough to help anyone."