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Waghorn, who scored 28 goals last term, already has four in three games this season

Rangers cruised into the last 16 of the Scottish League Cup with a fourth straight group win against outclassed League One Stranraer at Ibrox.

The visitors failed to cope with Barrie McKay, who was felled by the hapless Ross Barbour for an early penalty.

Martyn Waghorn dispatched it and plundered a Mark McGuigan back pass to add a second after 16 minutes.

The impressive Niko Kranjcar completed the scoring with a precise, controlled finish early in the second half.

Rangers might have added further goals but substitute Kenny Miller had an effort cleared off the line by Steven Bell and then diverted a James Tavernier cross wide from six yards.

But they comfortably maintained their 100% record and have yet to concede a goal after four competitive games, with the next round on 9/10 August.

McKay's menace leaves Stranraer stranded

Stranraer offered little resistance, passing the ball poorly and failing to close opponents down, and Kranjcar, Joey Barton - making his first start - and Andy Halliday controlled the game from midfield while operating at a low tempo.

The home side were capable of bursting into life, though, often when McKay was carrying the ball with impudence and menace towards the Stranraer defenders.

Quick and elusive, he glided past Barbour, whose instinctive reaction was to dive at the attacker and bring him down inside the penalty area.

Stranraer struggled to cope with the trickery and pace of Barrie McKay

Referee John Beaton pointed immediately to the spot and Waghorn converted, despite Stranraer goalkeeper Cammy Belford getting a hand to the ball.

The dynamic of the game was set, not least because the Stranraer players were unable to retain possession, much to manager Brian Reid's annoyance.

Waghorn might already have scored a second with a header before he gathered McGuigan's mis-hit pass and clipped a shot over the exposed Belford.

Kranjcar grows in prominence

With Barton dictating the pace and range of the home side's play from a deep role in midfield, Rangers racked up dominance and possession, although many of their efforts on goal were from long range.

Reid brought on Craig Malcolm and Kyle Turner at half-time, but the rhythm of the game remained unchanged. Waghorn almost completed his hat-trick only for the ball to be bundled clear as he was about to convert Halliday's cross.

Kranjcar celebrated his first goal since joining Rangers this summer

Kranjcar grew in prominence, and added the third when Waghorn brought a high ball under control and the Croatian midfielder drilled a perfect volley low into the corner of the net.

The Ibrox crowd got their first look at former Liverpool youngster Jordan Rossiter when he replaced Barton for his debut just days after returning from England duty at the Under-19s European Championships.

Kranjcar continued to spray passes around the field, and Miller scampered onto one, but Belford and Bell combined to block his shot before clearing.

Post-match reaction:

Rangers boss Mark Warburton: "The boys maintained the intensity, moved the ball well and created lots of chances, so overall it was a good night's work.

"That's four games, four clean sheets and 10 goals scored, so I am pleased.

"We have two days off now before we play Burnley [in a friendly at Ibrox on Saturday] which is very important after four games in nine days."

Stranraer boss Brian Reid: "We were a bit our own worst enemies at times and that start made it very difficult. But some of those boys only finished work at 5 o'clock so it is a good lesson for them.

"It could have been worse but we made a couple of changes, dug in and I felt we were a bit better in the second half.

"But you could see the difference in class with the players Rangers have got."