Near the end of Q2, Russell and Hamilton were starting flying laps when the former moved to the inside of the pit straight to grab a tow from Ferrari's Carlos Sainz, and then moved back onto the racing line.
But Russell appeared to be unaware that Hamilton behind him was also on a flyer and was about to overtake him on the outside when his team-mate inadvertently closed the door.
Hamilton had to take avoiding action with his left wheels on the grass, but still made contact with Russell and broke his front wing endplate in a collision that could have had much worse consequences.
On the radio, Hamilton said: "George just backed off, that was really dangerous."
The FIA stewards summoned both Mercedes drivers to review the incident, investigating why Russell's "car 63 normally changed direction directly causing impact with car 44" on Barcelona's start-finish straight.
When asked if the incident was simply down to a miscommunication, Russell said: "Yeah, pretty much. I wasn't even aware he was there.
"I was starting my lap, trying to take the slipstream from Sainz and fortunately, nothing bad happened."
The incident topped a messy qualifying session in which Russell struggled to get any grip from the tyres and faced a lot of bouncing. As a result, his 12th position on the grid was no surprise to Russell.
"I'm not too sure why straight out the box in run one I just had no grip from the tyres," he explained.
"I was really struggling, the car started to bounce a lot in the high-speed corners, so I couldn't take the [final] corner flat out when we were doing so this morning.
"A really, really odd session; not surprised to be out in Q2 because the car was just totally off the pace.
"I didn't have a good feeling with it. And yeah, disappointing for sure."
Russell said Mercedes did make some changes to the car ahead of qualifying but couldn't point to any reason why his W14 struggled so much on the low-grip track, which was swept clean by rain showers.
"We did change some things but nothing that we would have expected to have such a substantial effect," he continued.
"Maybe one thing I can contribute towards the lack of performance, it was clearly tricky for everyone out there.
"There were cars struggling left right and centre but, we shouldn't be out in this position. It's a bit of a shame."
