In 1998 Pagan Racing was left without a sponsor when the team's chief mechanic, John Barnes, formed his own team called Panther Racing using Pagan's former Pennzoil sponsorship. Guerrero drove the No. 21 Pagan Racing Dallara IR8-Oldsmobile Aurora Indy V8. At the season-opening Indy 200 at Walt Disney World Speedway Guerrero qualified 6th and finished 26th after retiring due to a crash after 13 laps. At the Indianapolis 500 Guerrero won the Scott Brayton Award for best showing the spirit of the deceased driver. In the race Guerrero started 9th and finished 22nd, 75 laps down. Following the True Value 500 at Texas Motor Speedway Pagan released Guerrero. Guerrero then joined Cobb Racing to drive the No. 23 CBR G-Force IR01-Nissan Infiniti Q45. Guerrero finished 4th at the Lone Star 500 at Texas Motor Speedway. Guerrero finished 26th in the championship with 83 points.