OXFORD United slipped back into the Sky Bet League One relegation zone as they began 2019 with a dire defeat at fellow strugglers Plymouth Argyle.

Karl Robinson’s side were booed off by the travelling support after a disjointed performance saw them lose for the third game running.

United trailed from the ninth minute, when a deflection fell for Antoni Sarcevic to slam the Pilgrims in front.

The visitors shrugged off the setback to carve out a handful of half-chances, without stretching Argyle goalkeeper Lyle Letheren.

But the key moment came five minutes before the break, when Ruben Lameiras doubled the lead after United lost the ball cheaply.

From then on a confident Argyle looked a cut above the U’s and the only surprise was it took until midway through the second half for Lameiras to bag his second goal of the game.

It leaves United firmly back in trouble after a miserable festive period undid much of their strong run before Christmas.

Illness ruled out Sam Long, so Jamie Hanson was brought back in despite him not fully recovering from a dead leg.

Robinson also changed his other full back, bringing Luke Garbutt in and pushing Josh Ruffels into midfield as John Mousinho dropped to the bench.

The Pilgrims began the day bottom of the table, but were ahead with their first meaningful attack, in the ninth minute.

A free-kick 40 yards out was squared to Ashley Smith-Brown, who was allowed to advance to the edge of the box. While his shot was blocked, the ball ricocheted for Sarcevic to volley in from close range.

It was a disastrous start in such a big game, but the visitors went on to get into some excellent areas around the Plymouth box.

Marcus Browne, who again looked well short of his best, had a great chance to equalise from James Henry’s 18th-minute cross, but on the stretch he could only steer the ball well off target.

Henry was the provider again just before the half-hour mark. He dug out a cross to the back post, where Browne nodded down for Jamie Mackie, whose low shot was saved by Kyle Letheren.

The goalkeeper also saved a long-range effort from Gavin Whyte, while Henry found the side netting from another half-chance.

But Plymouth went on to finish the half strongly, doubling their lead five minutes before the break.

There appeared little danger over a United throw-in near the halfway line, but they lost the ball and suddenly Freddie Ladapo was in space. He drew a challenge and laid off for Lameiras, who slotted into the net.

Simon Eastwood had been left exposed, but the goalkeeper did produce a stunning save to prevent United falling 3-0 down before the break.

A quickly-taken free-kick on Plymouth’s right found Graham Carey, whose curling 20-yard shot looked destined for the top corner before the goalkeeper got fingertips to the ball.

The hosts had their tails up and were getting in behind United at will, with Lameiras in particular looking full of confidence.

The half-time whistle brought a smattering of boos from the travelling fans and Robinson reversed one of his pre-match changes.

Mousinho was brought on for Garbutt, with Ruffels reverting to left back.

Plymouth remained on the front foot and Carey’s 54th-minute free-kick only needed a touch from Ryan Edwards or Ladapo to make it 3-0.

United’s big chance to get back into the game came on the hour. A long switch of play ran for Browne in the box, but a sloppy first touch saw the opportunity vanish.

Within minutes, what was left of the contest evaporated.

Referee Brett Huxtable played advantage after Mousinho fouled on the halfway line, allowing Lameiras to weave forward and fire a low shot into the far corner.

Argyle defended well in the latter stages as United pushed in vain to get on the scoreboard, but it was too little, too late.

Plymouth Arg (4-2-3-1): Letheren, Smith-Brown, Edwards, Canavan, Sawyer, Fox, Songo’o, Lameiras (Jephcott 90), Sarcevic, Carey (Wylde 89), Ladapo (Taylor 85).

Unused subs: Cooper, Moore, Wootton, Purrington.

Booked: Sarcevic, Carey, Sawyer.

Oxford Utd (4-3-3): Eastwood, Hanson, Nelson, Dickie, Garbutt (Mousinho HT), Ruffels, Brannagan, Henry, Whyte, Mackie, Browne.

Unused subs: Stevens, Raglan, Norman, Little, Spasov, Lopes.

Booked: Nelson, Brannagan, Dickie.

Referee: Brett Huxtable (Devon).

Attendance: 10,223 (534 visitors).