Mercedes team principal Toto Wolff has said Lewis Hamilton is a genuine threat for this year's title, saying of his former driver, "I know what he's capable of."
Hamilton won six of his seven titles with Mercedes under Wolff, but left for Ferrari in 2025 and on Sunday took his first victory for his new team at the Barcelona-Catalunya Grand Prix.
The win represented the first for a non-Mercedes driver this season and moved Hamilton 41 points off championship leader Kimi Antonelli, who replaced the seven-time world champion at Mercedes last year.
After five consecutive wins, Antonelli's title campaign stuttered on Sunday when he retired from the race with a power unit issue, and Wolff believes the momentum could easily shift towards Hamilton over the coming races.
"I'd rather not fight with him for a title, because I know what he's capable of," Wolff said when asked if he relished going up against his old teammate and friend. "If he smells blood, he goes.
"I've seen it many years where suddenly the Lewis Hamilton train started to go and then it's very difficult to stop it."
With 15 races to go this season, Hamilton sits between the two Mercedes drivers in the title standings, holding a nine-point advantage over George Russell in third place.
Asked if he saw the Ferrari driver as a genuine threat for the title, Wolff added: "Yes, absolutely. We're so early in the season and the gap is 41 points.
"You can see a DNF robs you of 25 points, and it's wide open. That's why we can't afford to not finish.
"And we need to just keep putting performance on the car and the power unit, not make mistakes, be clever with the strategy, and stay absolutely on it."
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Wolff and Hamilton forged a close bond over the 12 years they worked together at Mercedes and have credited one another for their personal successes during that time.
The Mercedes boss said he was "wholeheartedly happy" to see his former driver win in Spain and credited Hamilton's recent turnaround to a number of factors, and hinted at one of those being Kim Kardashian.
"Hard work and I think this is a car that is maybe different to the previous era cars with the bouncing, with the stiffness, maybe not easy to feel," he said. "This is back to more conventional driving in terms of, I would say, at least aerodynamics and vehicle dynamics.
"Obviously the engine management is completely different, but you can see he's driving strong. The dynamics in the team look to be good between him and his race engineer. I saw him on the podium on the telly, I mean, that face shows me that he's very happy. Maybe the girlfriend helps!
"It helped me to have a partner that, you know, you have a stable family life and they seem to be getting on really well. But I think it's all of those factors that put together the emotional and personal and professional perspective: if they are in a good place, you win."