Bob Jeffrey, who as a spotter won NASCAR Cup Series championships with Dale Jarrett and Tony Stewart, assisted in Danica Patrick's 2018 Indianapolis 500 sendoff and most recently served as Pato O'Ward's spotter the past two seasons, died Thursday after a battle with cancer.

"My spotter passed away today. Bobster, thank you for being a part of my journey," O'Ward wrote on Instagram Thursday evening. "I'm so glad I had a chance to say my goodbyes this morning. I know I'll have an angel riding alongside me forever.

"See you on the other side."

After serving as a mechanic and tire changer for various teams in NASCAR early in his career, Jeffrey jumped up to the spotters' stand to serve as the eyes in the sky for legendary driver Dale Jarrett during the driver's prime, including Jarrett's lone Cup title in 1999, a four-win season that included Jarrett's second of two Brickyard 400 victories.

Jeffrey continued working with Jarrett through the driver's retirement in 2008 before joining Tony Stewart as the driver joined longtime NASCAR owner Gene Haas to form the team now known as Stewart-Haas Racing. Shortly after Stewart and Jeffrey joined SHR in 2009, they landed the 2011 Cup championship — the third for Stewart and second for Jeffrey in a playoff run where the No. 14 Chevy won five of the final 10 races of the year.

After continuing to assist Stewart through the end of his Cup career that came to a close in 2016, Jeffrey joined forces with SHR driver Danica Patrick, who retired from full-time NASCAR racing in 2017 and then ran both the Daytona 500 and Indy 500. It was that edition of the Greatest Spectacle in Racing where Jeffrey first got acquainted in the IndyCar world — a fortuitous introduction that would lead his jobs for the final six years of his career.

In 2019, Jeffrey was hired by Team Penske to serve as Josef Newgarden's spotter, joining in time to help coach the No. 2 Chevy driver to his second career IndyCar championship. Newgarden would finish runner-up in the title race in each of the pair's next three seasons together (2020-22) before Jeffrey shifted over to O'Ward's No. 5 with Arrow McLaren to start the 2023 season.

Jeffrey fell ill in the leadup to this year's Indianapolis 500, spending part of qualifying weekend in the hospital, but he returned to his post in time to help O'Ward lead 11 laps down the stretch. He nearly clinched his first 500 winner's ring before Newgarden passed O'Ward in Turn 3 on Lap 200 and drove away for his second of back-to-back 500 victories. Jeffrey remained on the spotters' stand for O'Ward through the series' race at Laguna Seca June 23 before stepping away due to his health.

Though Jeffrey wasn't at the track, O'Ward won the next IndyCar race at Mid-Ohio, breaking an on-track winless drought that dated back to 2022 and delivering Jeffrey the first on-track win of his Arrow McLaren tenure.

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To celebrate him, Arrow McLaren says it will race with a special sticker on all three of their Chevy Indy cars during IndyCar's race weekend on the streets of Toronto this weekend, and O'Ward will sport one on his helmet too. The team will also place a headset on the railing of the spotter stand where he would've stood.

"We race for Bob this weekend," Arrow McLaren wrote on X after Jeffrey's passing. "Bob was a favorite in the paddock with his contagious laugh and brilliant personality. He is renowned as one of the greatest spotters in motorsport, having won championships in IndyCar, NASCAR and IMSA as the 'eye in the sky' for a number of first-rate racers, including Tony Stewart, Dale Jarrett and Josef Newgarden.

"Most of all, Bob will be remembered as a fun-loving family man who always greeted his teammates with a smile. We will miss you, Bob — forever our eye in the sky."

This article originally appeared on Indianapolis Star: NASCAR, IndyCar title-winning spotter Bob Jeffrey dies from cancer