Christian Horner is expecting Mercedes to be "quick" at the French Grand Prix, giving Red Bull a new but familiar rival this season.
Those two teams were the heavyweights last year, with Lewis Hamilton and Max Verstappen going toe-to-toe for the title. The Dutchman eventually wont hat duel, but Mercedes kept their grip on the constructors' championship.
This year the Silver Arrows have dropped away, with Ferrari taking their place as the team tasked with stopping Red Bull. Mercedes have been playing catch-up in terms of car performance, and it looks like their hard work might be starting to pay off.
Hamilton and George Russell have been more competitive in recent races and look to have closed the gap somewhat. Team chief Toto Wolff estimated that the W13 is still "two or three tenths" off the top two teams, but Horner is wary that Mercedes might already be a threat.
"We'll expect them to be quick at Paul Ricard," he said when looking ahead to the French GP. "They're showing flashes of being there or thereabouts. The last two races have been pretty decent for them and there's been no sign I think of any porpoising at all, so they seem to be slowly bringing themselves back into the game."
Their slow start to the campaign has given Mercedes a lot of work to do if they hope to still be in with a chance of silverware. The gap to Ferrari is 66 points and not insurmountable, but they are 122 points adrift of leader Red Bull.
Still, Horner refused to rule out the idea of the Silver Arrows being in with an outside change when it comes to the business end of the season. "I think they'll be a contender. They keep consistently scoring points," he added.
"I'm not sure how far off they are in the constructors' or drivers' [championships] at the moment, but you know, sometimes having more cars in play is a good thing. Sometimes it might be a bad thing. But I think for the fans it is great to have six cars, competing for victories."
His assessment comes after ex-F1 racer Jolyon Palmer said Mercedes are "dark horses" for the race win in France. "There are signs now, though, that they are getting on top of it and are merging back towards being genuine front-runners once more," he wrote in his column.
