Good enough for now, but Steve Johnson will need to lift his game if he plans on going deep at the ASB Classic.

The American, ranked 46th in the world, was handed a leg up when compatriot Ryan Harrison, who made the final of the Brisbane tournament last week, pulled out due to fatigue.

Italian 19-year-old Liam Caruana, ranked a lowly 397, stepped into the void and fought hard throughout the one hour 44 minutes.

Perhaps showing his inexperience, Caruana blew four second set points, allowing Johnson to close out the match in a tie breaker 7-5 7-6 (4).

Johnson, in his fifth visit to Auckland, came to the net regularly but struggled for accuracy and will need to improve to progress further than his semifinal appearance here last year, when he lost to Jack Sock.

The 28-year-old faces a difficult next match in fifth seed Roberto Bautista Agut, the Spaniard fresh off dispatching Kiwi Michael Venus 6-2 6-1 on opening night.

Bautista Agutv has won all four previous encounters with Johnson, the last of which was three years ago. Two of those matches went three sets, and their clash at Wimbledon lasted four.

"I've played him a few times and he's got the best of me every time," Johnson said. "I'm going to go out there and try do something different; do what we've been working on and hopefully change the outcome.

"A lot has changed since then so it's a good measure of how both of our games are and where we are to start the year. Hopefully I can build on today and keep getting better."

Earlier, Pablo Cuevas progressed to the second round in blazing hot conditions on centre court. The world No 33 was relatively untroubled against Taro Daniel (world No 98), easing to a 6-3 6-2 win in 76 minutes.