Martin Brundle has described Mercedes' 2022 challenger as a "complete mystery" after a rollercoaster weekend for the team in Miami.
Mercedes started on top at the newly-built Miami International Autodrome, leading the way in Friday practice as they trialled new parts and set-ups on George Russell and Lewis Hamilton's respective W13s.
But as qualifying and the race played out, Mercedes again found themselves significantly behind Ferrari and Red Bull, with Russell and Hamilton having to settle for the 'best of the rest' positions on Sunday in fifth and sixth.
Brundle: Mercedes have a good car, but it's well hidden
Looking back on the weekend in his column for Sky Sports, Brundle expressed concerns about the situation Mercedes find themselves in.
"Mercedes were once again the third-best team, but in many ways I think it was their most concerning weekend," wrote the ex-F1 driver turned pundit.
"George Russell was fastest on Friday and struggled for pace thereafter, and the team simply didn't know why.
"They've talked about 'diva' cars before, but this one is just a plain mystery with a knife-edge window of set-up.
"There's a good car in there somewhere, it's just so well hidden."
Viewed by others:
Brundle praises Russell: You make your own luck
Russell again finished as the lead Mercedes, keeping up his run of top-five finishes in 2022, having jumped Hamilton during a late Safety Car period.
However, Brundle hit back at suggestions that the young Briton was fortunate with his strategy, which saw him start on the Hard tyres and go long.
"It's easy to say Russell got lucky with the Safety Car," continued Brundle.
"He had to manage the Hard compound tyres from the start, keep his head when going further backwards a little, build the long-run pace as others started to fade, and then call the shots from the cockpit about staying out and hoping for a Safety Car."
Russell "coping better" than Hamilton amid struggles
Brundle then suggested that Russell is doing a better job of dealing with the predicament than the more experienced Hamilton.
Hamilton questioned Mercedes' approach over the radio during his battle with Russell, having been offered the chance to pit under the Safety Car.
"Lewis wasn't lucky with the Safety Car again, and on his side of the garage there was indecision rather than the usual masterly strategy we've become used to these past few years," he added.
"It's a tough time and eager George, with most of his career still ahead of him, is coping better with the situation than Lewis judging by radio transmissions."
Video: The 10 most bizarre F1 cars of all time
RacingNews365.com looks back at some of the strangest and most unique Formula 1 car designs from over the decades.