The Hawks dished out the first defeat of the season to the Dogs with a resounding 14.14 (98) to 7.14 (56) victory at Adelaide Oval on Saturday night.
Brilliant Bulldog Richards limped off in agony after his right ankle and foot twisted awkwardly late in the Gather Round game.
"We don't know the extent of it yet," Bulldogs coach Luke Beveridge said.
"We will have a look at it through the imaging and then we will ge back to you.
"We're just hoping it's not too bad but I can't give you anything until the medical staff give us something definitive."
The Bulldogs join Sydney, Fremantle and the Hawks with four wins and a loss, clear of the chasing pack.
Hawthorn co-captain Jai Newcombe produced the complete midfield game: 28 disposals, 14 clearances and a goal.
His co-leader James Sicily and Josh Battle both took 13 marks in defence, and Jack Ginnivan was a standout.
Ginnivan's 28 touches included a classy goal, while winger Karl Amon (24 possessions), Jarman Impey (26) and Blake Hardwick (25) were all prominent.
Mitch Lewis grabbed 10 marks in his imposing three-goal performance, and veteran Jack Gunston (three goals) and Dylan Moore (two) were other threats, but fellow forward Mabior Chol hurt a hamstring.
"We played with a level of intensity that is required to beat really good sides," Hawks coach Sam Mitchell said.
The Bulldogs, with Newcombe in charge and Hawthorn dominating stoppage clearances 34-16, struggled to assert customary midfield control.
Skipper Marcus Bontempelli (26 disposals) was busy, alongside Ryley Sanders (25 disposals) and Richards, who had 22 disposals and seven tackles before being hurt.
Ace attacker Sam Darcy kicked two goals, both in the first quarter - the first from a free kick, the second after a mark.
Hawthorn had the best of the opening term, with Lewis kicking two of four goals for a nine-point quarter-time lead.
The Hawks then put the squeeze on the Dogs, holding them goalless in a decisive second term to create a 28-point advantage at halftime, when prime mover Newcombe already had eight of his side's 22 clearances - the Bulldogs had only a dozen.
The Dogs, after blowing a series of set shots, reduced their deficit two minutes into the third quarter when Joel Freijah ran in to an open goal.
But the Hawks accelerated again with three goals in less than four minutes.
Livewire Nick Watson kicked one and set up another, and the influential Ginnivan's classy left-foot snap helped create a match-high 44-point break.
The Dogs appeared to be on canvas but were revived by young pups Josh Dolan, Harvey Gallagher and Cooper Hynes.
The inexperienced trio all slotted goals in a rapid retort from the previously unbeaten Bulldogs, who were 21 points down at three quarter-time.
But the Hawks expertly closed out victory before 48,481 spectators, kicking three consecutive goals before Bulldogs playmaker Richards hobbled off.
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