Throughout winter testing, the Milton-Keynes-based team projected itself to be within range of Ferrari and ahead of Mercedes however, after Friday running saw Mercedes' Lewis Hamilton top both sessions, Horner admitted that their pace looked stronger than his team initially anticipated.
“Mercedes looked quick in that second session, the times that both their drivers turned out looked pretty quick,” Horner told Sky Sports.
“Ferrari look like they underdelivered to what we thought they had in testing and our guys both had pretty decent runs.
“Max got quite a bit of traffic on his fast laps so I think there’s quite a bit of potential there, there’s more set up changes to come and we don’t know what fuel loads people are running but looks interesting.
“On the long runs we look pretty sensible and I think the one lap pace of the Mercedes in that session looked pretty impressive, but the car looks stiff and difficult to drive so whether that’s sustainable for a grand prix I don’t know.”
It isn't just over one lap that the Silver Arrows appear to have the edge. Long run pace from both Hamilton and Valtteri Bottas put them ahead of Red Bull and Ferrari going into Saturday, with the latter two with a long night ahead in Melbourne and back at base if they are to overturn the performance gap.