MIAMI -- Mercedes boss Toto Wolff described his team's car as "a nasty piece of work" after Lewis Hamilton qualified 13th for Sunday's Miami Grand Prix.

Mercedes struggled throughout qualifying Saturday, with Hamilton missing out on a place in Q3 and George Russell securing sixth on the grid after benefitting from a late red flag.

"I take no enjoyment from finishing sixth, because probably sixth should have been eighth or seventh, and even if it was fifth, I would take no enjoyment," Wolff said. "It's more about the lack of comprehension of what it is that makes this car such a nasty piece of work."

He added: "I think that the car is not a nice car, not a good car, and I wouldn't even be able to point out where the issue is because it's everywhere. The basic performance of the car, the lack of understanding of the car is through the whole span of activities on this track. The performance is just really bad."

To compound the issue, Hamilton said he was sent out on the track too late to properly prepare his tyres for his final attempt in Q2.

"It started out OK -- there were a couple of decent moments throughout the session," Hamilton said. "We've generally struggled to have the true pace to get into Q3 today, maybe on the cusp of not getting in, then right at the end we went out too late. I was at the back of maybe seven cars and started the lap with just not enough temperature in the tyres."

Mercedes is planning to bring a major upgrade to its car for the next race at Imola, including new front suspension and revised sidepods. Wolff said he believes the upgrade could make the car easier to drive but warned against expecting too much.

"I don't believe in miracles, but I think the stability of the car and the predictability is just subpar," he said. "If you can sort that out, helped by a front suspension redesign, then that is definitely a good avenue, and as you say this can be more than a tenth or two of lap time than the aerodynamic package brings, and this is simply because we will have much more drivability and pace."

Wolff added: "I think what we are trying to do with the upgrade is to create a new baseline for us to take question marks and variables out of the equation and say this is not a problem now that we have come to a different spec, for example, front suspension.

"We are also looking at bodywork solutions that are more conventional than others, and that will create a different airflow. So for me, that is almost like a reset with what would have been a good start 12 months ago and then try to add performance. But the moment it is just a lack of understanding."