The champion jockey had already ridden a double at the West Yorkshire track – he had to be at his brilliant best on both Petticoat Tails and Dalaman – before being unseated from the Kerry Lee-trained Grey Gold and landing awkwardly.
A runaway winner of the last two title races, Johnson is only 18 clear of Harry Skelton, his closest pursuer, and will not want to spend too much time on the sidelines.
“If you get concussion you are off for a mandatory seven days, which means Tuesday is the earliest I can return unfortunately,” said Johnson, who is on the 123-winner mark for the current campaign.
“It’s really frustrating to be missing out on Newbury on Saturday and Cheltenham on New Year’s Day, especially as I feel absolutely fine.
“I understand that safety has to come first, though, so I just have to sit and suffer.
“The earliest I can do the baseline test is Monday, so I might be riding at either Ffos Las or Ayr on Tuesday.
“It’s not a time of year you want to be off, but it could be a lot worse.”
The only consolation for Johnson is the freezing weather as Britain’s latest icy blast takes its toll on the racing programme. Today’s meeting at Doncaster must pass an early morning inspection.
This said, Johnson hopes to be fit to ride Rock The Kasbah in the rearranged Welsh National at Chepstow on Saturday week – weather permitting.