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Larson, the reigning Cup Series champion, went out late in the 35-minute session for a flying lap and posted an average speed of 181.183 mph. Larson won the first of his 10 races last season at Las Vegas.
Christopher Bell ended up second-fastest (180.771 mph) and Ryan Blaney third (180.000 mph.) William Byron was fourth and Joey Logano rounded out the top-five.
Completing the top-10 average speeds were Alex Bowman, Tyler Reddick, Chase Elliott, Daniel Hemric and Ross Chastain.
Larson also had the fastest average lap speed (178.981 mph) among those drivers who ran at least 10 consecutive laps. Byron and Blaney were second and third, respectively, in that category.
Just over six minutes into the session, Kyle Busch appeared to have a left-rear tire go flat as he entered Turn 3, he spun and backed his No. 18 Toyota into the wall, suffering a good bit of damage.
‘I was just running around there making laps,” Busch said. “I got a little crossed up off of (Turn) 2 one time but never heard anything that I did anything or anything like that.
“Was going down the backstretch, felt it start to go down. It happened so fast, it was too late to slow down to do anything. Sucks for all the guys. I hate it for everybody at Joe Gibbs Racing. What do you do? When they don’t hold air, you can’t make a corner.”
Busch will move to a backup car and will have to start Sunday’s race from the rear of the field regardless of where he qualifies on Saturday.