The 29-year-old said that while his club still trained at a high level, standards had dipped, which was reflected in the club's inconsistent start to the 2013 season.
The Crows looked a more capable unit against Hawthorn last weekend and hit the lead in the final term only to let the game slip away by the final siren.
Midfielder Rory Sloane said his team was beginning to return to the standard it set in 2012, but Reilly said to make sure it reached and maintained it, training standards had to lift.
"If you don't do that, you're not preparing yourself right for the upcoming game every weekend," Reilly said.
"We need to lift our standards up on the track. [I'm] not saying they're poor, but we just need to get back to that training standard we had last year.
"It's probably showing in our game we're not doing that consistently enough.
"We know what works and that's what makes us play well."
Reilly and the Crows face Greater Western Sydney at Skoda Stadium on Sunday, a side more than capable of catching rival clubs unaware.
The AFL's newest team stunned Essendon on Saturday with a five-goal first term and an incredible upset loomed when they carried a significant lead into the main break, before the Bombers piled on the goals in the second half.
The Giants' message was heard loud and clear by Reilly, who claimed his side was in no position to even think about resting players.
"Not when we're out of form – we need to win games of footy, we can't afford to rest our key players," he said.
"We've never been complacent about GWS, they're a good young team and they've taken it up to teams in the first half of every game this year.
"They're going to come out firing and we need to be prepared for that, go up there and have a good win."
Harry Thring is a reporter for AFL Media. Follow him on Twitter: @AFL_Harry.
