Hendrick Motorsports teammates William Byron and Chase Elliott were fastest in the opening round of practice at Phoenix.
Byron jumped to the top of the leaderboard late in the 50-minute session. His fastest lap was 134.595mph (26.747 seconds). Elliott had previously put down the fastest lap at 133.849mph.
Third fastest was Brad Keselowski at 133.309mph. Clint Bowyer was fourth fastest at 133.235mph with Kurt Busch fifth fastest at 133.220mph.
Defending race winner Kyle Busch was sixth quickest at 133.156mph. Rounding out the top 10 was Joey Logano at 133.062mph, Kevin Harvick at 132.959mph, Erik Jones at 132.768mph, and Ryan Blaney at 132.641mph.
Rookie Tyler Reddick, who was 13th quickest, ran the most laps in practice at 34. Ross Chastain was 14th fastest in the No. 6 Ford for Ryan Newman.
Corey LaJoie tagged the Turn 1 wall with the right rear of his Ford Mustang. When rookie Quin Houff merged back on track, it resulted in LaJoie getting into the corner higher than he wanted to, and LaJoie was already loose on entry. His Go Fas Racing team is attempting to repair the car to avoid pulling out the backup.
In the best 10 consecutive lap average Tyler Reddick was fastest over Martin Truex Jr., Kyle Busch, Chase Elliott, and Kurt Busch.
UP NEXT: Final practice at 5:35 p.m. ET.