Hamilton was 0.829s off the pace set by Ferrari’s Charles Leclerc in Saturday’s qualifying as he finished sixth, while Russell exited in Q2.
It had previously appeared like Mercedes might have a promising weekend with a solid Friday practice after their poor start to the 2022 campaign.
Seven-time world champion Hamilton told Sky: “I had a much better qualifying session than I’ve had for the past three races so I am grateful for that.
“I’ll take it. We will keep on chipping away. Keep working at it.
“There is so much amazing work going on in the background. Everyone is working so hard.
“Unfortunately I don’t think we are necessarily moving forwards at the rate that we would like to.
“The gap is similar to what it was at the start of the year.
“Eventually, we will get there.
“It has not felt better this weekend. But once I got the tyres into a better place, it was a little bit better.
“Race pace? I have no idea.”
Can Mercedes fix issues before F1 Miami GP?
Mercedes team principal Wolff added to Sky: “We were completely off with the experiments that we did.
“The car is still bouncing like a kangaroo.
“The drivers are not happy with it.”
Russell said: “The car felt different today than it did in FP2. The car struggled today with porpoising. I couldn’t attack any of the corners. There was potential there. We were quick but it got away from us today. I don’t know what happened.
“It is inconsistent. We thought we were conservative to avoid porpoising. It doesn’t make a lot of sense at the moment.
“Yesterday we looked like we were in a fight for pole and today we qualify P12 which is our worst of the year.
“The performance is flip-flopping.
“I am disappointed to miss out on P3.”
Hamilton criticises FIA jewellery ban
The FIA have emphasised that watches are part of their jewellery ban – a day after Lewis Hamilton arrived at the F1 Miami Grand Prix wearing three watches.
“In the interest of safety, watches will be considered as jewellery,” a new note from race director Niels Wittich said on Saturday.
Hamilton had turned up to Miami decorated by jewellery including eight rings, four necklaces, two earrings, a bracelet and three watches.
He has a two-race exemption for Miami and Spain for his nose ring which he says cannot be removed, but he did show some compromise by removing his ear piercings on Friday after a meeting with FIA president Mohammed bin Sulayem.
Drivers will reportedly face a major fine and even a points deduction if they do not comply with the FIA’s rules.
“What was needed was a dialogue between Lewis and Mohamed,” Mercedes team principal Toto Wolff said.
“It is clear the regulations are to protect the drivers.
“I am sure they will come to a good resolution.”
Hamilton previously said about the new FIA rules on wearing jewellery: “I feel like it’s almost like a step backwards, if you think about the steps we are taking as a sport, and the more important causes that we need to be focused on.
“I think we’ve made really great strides as a sport. This is such a small thing. I’ve been in the sport for 16 years and I’ve been wearing jewellery for 16 years. In the car I only ever have my earrings on and my nose ring, of which I can’t even remove.”