Fremantle won their eighth straight match on Sunday, beating Greater Western Sydney by 76 points at Patersons Stadium, to climb to second on the ladder behind the Sydney Swans with matches to come against St Kilda and Carlton either side of the bye.
Despite their position on the ladder, Lyon thinks his side still has some major tests to come before they can be considered genuine premiership contenders.
"What we've spoken about internally is we've tracked along OK but earlier in the year Port Adelaide beat us, Sydney beat us, and Hawthorn," he said on 6PR on Monday night.
"In the ensuing weeks we play Geelong, Hawthorn, and Port Adelaide, three of the top five.
"So until we beat those teams our credentials aren't as solid as we would like them.
"When you look at Sydney and Hawthorn they've been able to beat us and Port have beaten teams around the top of the ladder.
"Our big challenges are coming. We might sit second but in reality I think we've still got to prove some of our bona fides.
"That's the way we're thinking internally, the players and the coaches."
Fremantle have had some injury concerns in recent weeks but will get some key players back before September.
Luke McPharlin is likely to return this week after missing the win over GWS with a minor calf strain.
Matt de Boer is producing some excellent form in the WAFL coming back from a medial ligament strain.
Lyon said Alex Silvagni has been cleared to resume training after suffering a collapsed lung following a heavy hit in the win over Richmond in round 13.
Michael Walters is edging closer to a miraculous comeback from ankle surgery.
"Walters is running," Lyon said.
"He's probably a few weeks away from resuming."
Stephen Hill is expected to return from a quad injury after the bye, while Garrick Ibbotson's calf injury may take three to four weeks to heal.
Scott Gumbleton hurt his back last week and didn't play in the WAFL on the weekend while Kepler Bradley injured his hamstring in Peel's win over Claremont.
Youngster Brady Grey has been ruled out for the rest of the year with a stress fracture in his back.
