Andretti Autosport’s Alexander Rossi has set the fastest lap in an opening IndyCar practice session at Toronto which was disrupted by four red flag periods.

Team Penske drivers Scott McLaughlin and Will Power both seemingly got away with swiping the outside rear wheel on the wall, at Turn 11 and Turn 8 respectively, but three drivers found themselves in greater trouble, to varying degrees.

Callum Ilott fared worst, missing the latter half-hour of the 75-minute Practice 1 session at Exhibition Place after clouting the wall exiting Turn 1.

Rossi would finish quickest in the #27 Honda with a 1:00.6090s once he had swapped to alternate compound tyres, ending the hit-out less than a tenth of a second up on Meyer Shank Racing’s Simon Pagenaud and Rahal Letterman Lanigan’s Graham Rahal.

While the rookies were out first, as usual, Chip Ganassi Racing’s Alex Palou joined them earlier than the rest did in cutting laps.

The Spaniard at the centre of the remarkable contract wrangle involving McLaren Racing would enjoy several minutes on top of the timing screen when he clocked a 1:01.8398s and 1:01.4782s, either side of the 15-minute mark.

Not long before the first half-hour was done, Power moved the marker to a 1:01.3240s and then Rossi to a 1:01.3068s, still on primary tyres.

Felix Rosenqvist (McLaren SP) was fastest on a 1:01.3015s by the time a red flag was called in order for IndyCar officials to inspect a manhole cover at the exit of Turn 1, before the green flag came again in the 38th minute.

Rahal took over the ascendancy with a 1:01.2819s, about a minute prior to the second red flag of the session, 45 minutes in.

Ilott was the cause, the rookie getting loose through Turn 1 before smacking the wall with the left-front corner of the #77 Chevrolet.

The field had only been going for another three minutes when Jimmie Johnson (Ganassi) spun at Turn 8 and hit the wall with his front wing, necessitating a third red flag period.

The following restart, with 16 minutes to go, marked a wholesale switch to alternate compound tyres, helping Palou to go back to the top when he laid down a 1:01.1376s.

Rosenqvist reset the fastest lap when he clocked a 1:00.7936s in the final 10 minutes, but that was beaten when Rossi went to a 1:00.6090s.

There was yet another red flag in the 72nd minute when Helio Castroneves (MSR) nosed into the tyre wall at Turn 8, as Scott Dixon (Ganassi) headed up the run-off area just ahead of him.

A final restart came with a touch under two minutes left before the chequered flag, but the top end of the timing screen remained unchanged thereafter.

Rossi thus held sway while Pagenaud had moved into second with a 1:00.6991s moments before his team-mate came unstuck.

Rahal would be 0.0040s slower in third on a 1:00.7031s, from series leader Marcus Ericsson (Ganassi) on a 1:00.7262s and Josef Newgarden (Penske) on a 1:00.7650s.

Rosenqvist ended up sixth on his aforementioned lap time, from Colton Herta (Andretti Autosport w/ Curb-Agajanian), Dixon, Power on a 1:00.9932s, and Palou in 10th, while McLaughlin finished 15th-fastest on a 1:01.3171s.

Practice 2 starts on Sunday morning at 00:00 AEST, ahead of Qualifying at 04:00 AEST, with both of those sessions live and ad-free on Stan Sport.

Results: Practice 1