Mika Hakkinen has voiced his concerns for Max Verstappen's championship prospects after the Dutchman suffered another mechanical failure in the Australian Grand Prix.
Verstappen recorded his second DNF of the season when he was forced to pull to the side of the track on Lap 39 of 58.
Meanwhile, it was a smooth drive to victory for Charles Leclerc, who has now extended his lead at the top of the World Championship standings to 34 points ahead of George Russell in second.
Hakkinen admits that the Ferrari driver was in an ideal situation, with the car performing just as he wanted it to.
"There is so much to take away from this race," Hakkinen wrote in his column for Unibet.
"Charles Leclerc was in complete control and said afterwards that the car felt really strong, using its tyres well and giving him a really consistent performance.
"That's what any top driver wants - a car that's quick from the start to finish and responding to all your inputs."
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Hakkinen: Verstappen will not be happy
Leclerc is clearly in a good place as he continues to mount his title challenge, but Hakkinen acknowledges that the same cannot be said for Verstappen.
The Finn admits that Red Bull's recent reliability woes are not acceptable when fighting for a World Championship.
"What's important is that Charles has taken two wins and a second place from these first three Grands Prix, while Max Verstappen has had one win and two non-finishes," Hakkinen commented.
"At this level you cannot afford to have constant technical failures. Max will not be happy."
Verstappen has labelled his retirement in Melbourne as "pretty frustrating and unacceptable."
His teammate Sergio Perez - who, along with Verstappen, recorded a DNF at the season-opening Bahrain Grand Prix due to a mechanical issue - has also admitted that the Milton Keynes-based outfit "got a few things quite wrong, fundamentally" in Melbourne.
F1 Podcast: Can fast but fragile Red Bull respond to Leclerc's charge?
RacingNews365.com F1 journalists Dieter Rencken, Mike Seymour and Thomas Maher look back over the Australian Grand Prix, where Ferrari's Charles Leclerc triumphed and Red Bull's Max Verstappen retired.