The 29-year-old Republic of Ireland international struck after 40 minutes to cancel out Matty Robson's opener for the League One side, and then doubled his tally seven minutes after the break when he converted debutant Danny Guthrie's through-ball.

Former Liverpool midfielder Guthrie, a half-time substitute, marked his first appearance for the club with a deflected third seconds later, but it was Duff who claimed the headlines with a deft 88th-minute finish to impress his manager.

Keegan was delighted with his contribution, which suggested he is finally ready to reproduce his best form after an injury-hit first two years on Tyneside.

The manager said: "He looks very sharp. It's the first time in three or four years that he has had a pre-season.

"He has missed all pre-season training in the last three and any pro will tell you, that is of major importance to get that in because it gives you a base for the season.

"He has looked very sharp. He says his weight is down to what it was when he was 17, 18, and he looked like a 17 or 18-year-old out there.

"He was very good and the three goals were nice to see. He has worked very, very hard, as have all the players."

Keegan admitted he arrived at Victoria Park with limited outfield options as Michael Owen joined Mark Viduka on the sidelines with a sore calf muscle, while Steve Harper and Habib Beye were also missing with Abdoulaye Faye and Geremi having been given extended summer breaks.

New signing Jonas Gutierrez was in the stands as he waits for his registration to be processed, but fellow recruit Guthrie did get his chance.

Keegan said: "He was very good. I wanted to play him from the start, but he has just had a little bit of a problem. They do get a lot of niggles at this time of the year.

"He has had a little bit of a problem with sore shins, so we just backed off.

"But he came on for the second half and within four or five minutes, he had made a goal and scored a goal.

"I think he will be a tremendous asset to us. He is a typical Liverpool player, he passes the ball really well and you don't see him give it away very often.

"The goal was probably a bonus."

The game came with the Magpies' recruitment department still scouring the globe for signings, and their need to make several more breakthroughs was reflected by their bench.

Of the nine substitutes named, only Guthrie and Shola Ameobi have any Premier League experience, and Keegan admitted the need for more bodies is pressing.

He said: "There have definitely got to be some more in the pipeline. We only had two players (on the bench) today who I would call senior players with us, so that gave us a total of 12 outfield players.

"We are like a lot of clubs at the moment, everyone is waiting for something to happen. We are still looking.

"They will definitely be in by the end of the transfer window because you just can't go into the Premier League with this small squad we have got.

"But everyone is working hard and we will see what happens."