"Of course you never know what your opponents are up to and there's quite a bit of gamesmanship that goes on at this time of year.
"But we'll soon know ... where the pecking order is."
Webber won just one GP last season - the final race in Brazil - while teammate Vettel swept to 11 victories and a landslide drivers' championship victory.
Now 35, Webber has seven career GP wins and status, but time would appear to be running out if he wants to fulfil his dreams of winning in Australia.
He faces his toughest battles this season from within, as Vettel should remain the sport's dominant force if the RB8 rolls out of the box with speed.
And young Australian Daniel Ricciardo is auditioning as perhaps Webber's long-term replacement, driving this season with Red Bull's B-team Toro Rosso.
Helping Webber's cause will be changes to tyres - his biggest source of on-track problems last year.
Manufacturer Pirelli has made its dry weather tyres softer and attempted to narrow the gaps in life between its four compounds - great news for Webber who struggled badly with tyre life last year.
In Melbourne, drivers will be able to choose between medium and soft compounds for their dry tyres.
Horner sees McLaren's Jenson Button as the biggest threat to Red Bull this season.
McLaren showed big improvement in pre-season testing and rival drivers also suggest they and Red Bull are the teams to beat.
Crews have started to assemble in Melbourne for the GP, with the majority to arrive by today.
- AAP