It’ll be no surprises when Canadian Vasek Pospisil takes on doubles partner Jack Sock in the second round of the ASB Classic.

The 25-year-old on Monday pipped tournament 7th seed and world No. 23 Ivo Karlovic 7-6 7-5 in a tightly fought first-round match.

Dominated by serves, and featuring few returns and fewer long rallies, the two went neck-and-neck to a first-set tie-breaker – Pospisil managing to clench it.

But in the second, the Canadian, ranked No. 39, produced the game’s only break, at five games each, to seal the match on his next serve.

Pospisil will now faces his doubles partner, American Jack Sock, world No. 26, who earlier swept to victory in two quick sets against Dominican Victor Estrella Burgos.

Sock, 23, quickly dispatched world no. 56 Estrella Burgos, 35, 6-0 6-4 in just 49 minutes.

He and Pospisil have won four doubles ATP trophies, most recently the Beijing Open in 2014.

After the match, Pospisil said he was hoping to take the dominant serve game from Monday’s game to Sock.

“He’s a dangerous player, I obviously know him quite well. No surprises there.”

“He’s got a great forehand, and he’s going to play to my strengths, but serving well is going to be key,” he said.

Earlier, 24-year-old Australian Matthew Barton, ranked 299 in the world, beat American Steve Johnson 6-3 3-6 6-3 in the biggest upset of the competition’s first day.

He took a commanding lead after five games in the first set, carried by a consistently strong serve, including 13 aces for the game.

Barton will now face tournament top seed and world No.7 David Ferrer in the next round.

After the match, he described the win as an “unreal experience”.

“I got lucky really. I got some lucky returns. But I was working, really focusing on those big points, Barton said.”

Meanwhile, New Zealand No. 1 Finn Tearney made a swift exit from the Classic, losing in 6-2 6-3 to world No. 48 American Donald Young.

Tearney had a stellar run last in the ATP year, rising more than 1000 ranks to reach his current world ranking of 363.

Afterwards, he said he wasn’t deterred by the loss and still had his eye on a top-tier ranking.

“I love tennis, that’s what I want to do, but I don’t want to sit back and play minor league tennis until … anymore, really,” he said.

His loss leaves wild card Michael Venus as the only New Zealander remaining in the tournament.