Hardwick also put the heat on his midfield to step up when skipper Noah Anderson next cops a tag.
The Suns (3-2) were outmuscled by Sydney in Saturday's 14.16 (100) to 9.14 (68) defeat at Norwood Oval.
Hardwick was left to lament Gold Coast being unable to unsettle Sydney, and struggling with the Swans' pressure when they did get the ball.
"To me, this is a side that had a blip on the radar, I reckon, last year (when Sydney missed the finals). They're a very good side," he said.
"We sort of have them ranked very, very highly. They're playing some really, really good footy, and the fact of the matter is there's a gap between us and those sides at the moment.
"I shouldn't probably say this, but I think they're a top four quality side. Once again, they've got a really established core group of players that play a great style of footy, and we've got to close that gap. We're not there yet."
Petracca (hamstring) and Humphrey (suspension) will be welcome additions against Essendon.
Anderson was blanketed by James Jordon on Saturday, and Sydney's midfield, led by the exceptional Isaac Heeney, clearly won the day.
"It's an important thing," Hardwick said.
"Players are going to get shut down, but I think personally we've got enough calibre players that should be able to stand up and rise.
"Obviously we get Humphrey back next week and Petracca back next week, which will certainly help. It gives us a few more magnets that we can put through there.
"But the other guys, and credit where credit's due, Touk (Miller) and Rowelly (Matt Rowell) and all those guys took it on board and they've got to get better in that facet of the game.
"Guys are going to get sat on at various stages, but one player being tagged out of the game shouldn't cost us a game."
After Mac Andrew showed some "damaging" signs in the ruck against Brodie Grundy, finishing with 17 disposals, 11 hitouts and six marks, Hardwick indicated the Suns would explore testing the talented tall there more often.
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