Following the conclusion of the second week of pre-season testing at Barcelona, Mercedes and Ferrari emerged once again as the two strongest outfits.
While Red Bull had been harbouring ambitions of taking the fight to the 2015 pacesetters, Riccardo says the best the team can hope for is to be third in the pecking order in Melbourne.
Asked if he was only likely to be a podium contender on low-speed tracks, he said: "If we raced tomorrow, that's probably where we stand for now.
"From that, I mean Mercedes are Ferrari are ahead on pure pace right now - it's evident but also expected.
"If we raced in Monaco, we could have an outside chance of a podium, but here we'd need a little a bit of luck."
He added: "I think the car is better than it was 12 months ago, so we should do better [than last year], but then again Williams and Force India have also improved a chunk.
"The battle for fifth will be pretty close, but all going well we can hopefully pull it off."
More to come
Ricciardo also conceded that the hoped-for gains that Red Bull had been anticipating last year had not materialised – but hoped further progress can be made over the course of the season.
"There's always more to come, but I don't think it's that chunk we were hoping for 12 months ago," admitted the Australian.
"At the end of last year, the car was pretty good on most circuits, it could be better on some, but I think that's where we stand now.
"Melbourne will be a whole new ball-game for everyone, but we're in a good position chassis-wise."
This article by Jamie Klein originally appeared on Motorsport.com, the world's leader in auto racing news, photos and video.