World number one Brooks Koepka marked his return from injury in ominous fashion with an opening 66 in the Abu Dhabi HSBC Championship.

Koepka, who has not played since October, showed no signs of rust as he carded six birdies in a bogey-free round to lie two shots off the early clubhouse lead held by Italy's Renato Paratore.

The four-time major winner had stem cell treatment on his left knee at the end of August but aggravated the problem after slipping on wet concrete during the CJ Cup in South Korea and was forced to withdraw from the United States team for December's Presidents Cup.

"It's good to be back," Koepka told Sky Sports. "I missed the competition obviously.

"Played really solid. Missed a few putts early if I really want to pick it apart. Drove the ball well. Controlled ball flight and controlled distances really well and that's what you have to do out here.

"Usually in the afternoon the wind picks up and you know that going in so when you have a morning tee time, you have to take advantage of it. I did that today.

"Hopefully tomorrow the wind stays down a little bit because this golf course into the wind, or with the wind, can be very difficult."

Asked about his knee, Koepka added: "It feels fine. It was a little sore last night. That's expected. This is the first week I've walked 18 holes and I've done it three times already. It's a little tired."

In the week when the European Tour's bid to stamp out slow play came into force it felt fitting that Paratore, who is renowned as one of the quickest players in the game, set the early pace with a superb 64.

The 23-year-old ended his round with four straight birdies to enjoy a two-shot lead over Koepka and Australia's Jason Scrivener, with Sergio Garcia a shot further back and defending champion Shane Lowry carding an opening 70.

"Today the short game was really good and also the iron play," Paratore said.

"I made some good putts the first few holes so that give me good confidence for the rest of the day, and I keep making putts, so it's been a really good day."