Horner reckons Ricciardo has the right mindset to race for Red Bull, and will be capable of replicating his stellar 2013 qualifying performances for Toro Rosso, where he regularly got a midfield car through to the final segment of qualifying.
10 reasons why Red Bull signed Ricciardo
"I think he could be a bit of a surprise because he is very quick," said Horner.
"He is going to have a lot to learn but I think he will surprise quite a few people with the pace he has.
"He has dragged massive qualifying performances out of the Toro Rosso, which obviously is sub-standard, and he has continued to impress us with how he has raced, how he has delivered and performed with the tools at his disposal.
"If you look at the pressure points with him, even if his weekend doesn't get off to a great start he recovers it.
"He seems to have the ability not to panic, but to put it together when it counts.
"Sometimes he's had difficult Fridays, or even Saturday mornings, but when qualifying starts, nine times out of 10 he is there."
Horner also expects Ricciardo will not find it difficult to settle in with his new team, despite the distraction of massive rule-changes for 2014.
"It is probably the right time in many respects," added Horner. "It's a change in so many aspects that now is the time to change the driver.
"Of course, he is pretty well known to us anyway so it's not like introducing a complete stranger."