Rory McIlroy said it has been a "nice start to the year" as the four-time major winner contends at the Tournament of Champions.

McIlroy usually starts the year on the European Tour but the former world number one opted to kick-off his campaign on the PGA Tour via the Tournament of Champions, where he is three shots off the pace.

The Northern Irish star carded a second-round 68 – which included six birdies and four from his final seven holes – to be within striking distance of leader Gary Woodland at the halfway stage on Friday.

Speaking afterwards in Hawaii, McIlroy said: "It has been a nice start to the year. It is something to build on going into the weekend.

"I just need to keep hitting good golf shots and giving myself chances."

McIlroy added: "I've enjoyed the last couple of days, flighting different shots, hitting different trajectories.

"With all the technical work I've done in the off-season it's a real contrast to come out here and completely forget about the swing and just hit the shot."

Meanwhile, defending champion Dustin Johnson was hit with a two-stroke penalty for hitting the wrong ball, leaving him with a double bogey.

American star Johnson finished the day with a one-over par 74 as he dropped 10 places to five under.

"Obviously it was my fault. The marshal had it marked, said it went in the hazard right there, and there was a ball right there and it was a TaylorMade. I could see the logo on the side, so I obviously just assumed it was mine," Johnson said.

"That won't ever happen again. I can promise you that. It's just bad luck."