In Sunday's Baku race Russell had to take avoiding action on the lap 13 restart not to hit Aston Martin's Fernando Alonso into Turn 1.
Russell had to veer right, which made him miss the apex of the 90-degree left-hander and left him wide onto the dirt on exit.
That gave the chasing Lance Stroll the momentum to pass him for seventh place on the inside into Turn 2. Stroll's move also backed up Russell enough to allow team-mate Lewis Hamilton past in the run to Turn 3.
It was the second day in a row Russell made a poor restart after being picked off by Max Verstappen at the line in Saturday's sprint restart.
"I'm a little bit disappointed with myself," Russell said. "I made a really good start, got into good position around the pitstops to get ahead of Stroll and then I just made a mess of the restart.
"I was defending from Lance, almost went into the back of Fernando, ran wide got my tyres dirty, which is ultimately the reason why Lance and Lewis got by and from then on it was the line astern.
"I just got a bit caught out about how early Fernando braked, I had to almost go to the right in Turn 1 instead of turning left, got onto the dirt and it just all went downhill from there.
Source: Autosport