HE might not have covered himself in glory since arriving on Tyneside two summers ago, but Alan Shearer last night admitted that Jose Enrique is the one player Newcastle cannot afford to lose between now and the end of the season.

After missing the last two matches with a knee injury, Enrique will return to firstteam action in Monday’s crucial relegation encounter with Portsmouth provided he comes through two full training sessions unscathed this weekend.

The Spaniard’s absence has caused havoc in recent weeks, with Shearer switching to a three-man central defence at Stoke and Spurs in an unsuccessful attempt to negate the loss of the club’s only recognised left-back.

For most of his Newcastle career, Enrique, a £6.5m signing from Villarreal, has been viewed as an expensive flop.

But for the final five games of this most traumatic of seasons, the full-back finds himself feted as United’s most important player.

“If Jose had been fit, I wouldn’t have made the changes I’ve had to make,”

said Shearer, who will revert to a flat back four on Monday night. “If our left-back had been fit, he would have been playing at left-back. Simple as that.

“It’s posed a major problem for us, because our one and only left-back has not been available. As a result, we’ve had to ask players to play out of position and go with different formations to what we would otherwise have gone with.

“From that point of view, losing Jose was just about the worst thing that could have happened. If you’ve only got one left-back, you can’t afford to lose him.

“But we’re hopeful he’s back now. He hasn’t fully trained, but he’s been working with the physios all week and that’s gone well. He’s been stepping things up, and if things go well (today), hopefully he’ll join in full training with us on Saturday.”

Joey Barton is also expected to resume full training at the weekend, and the midfielder could find himself on the substitutes’ bench against Portsmouth if all goes to plan.

The controversial midfielder has been sidelined since breaking a metatarsal in January and while, like Enrique, he has flattered to deceive since moving to the North- East, Newcastle have unquestionably missed his drive and creativity in recent matches.

Shearer has been impressed with Barton’s attitude since taking over at the end of last month, and feels the England international could yet have an important part to play in the final five weeks of the season.

“Joey could do a big job for us if he was fit,” said the Newcastle boss. “We’re trying everything to get him fit but whether he’ll make Monday, we’ll have to see.

“I’ve had no problems with him at all since I’ve been here.

Whatever we’ve asked of him, he’s done fine.

“He’s desperate to play football, that’s what he wants.

He’s fed up of being injured – he wants to go out and he wants to play. But there’s no point pushing him to the extreme.

We don’t want to be pushing him so much that we cause a setback. We want him fit, but when he is handed over to us for matches, we want him to be right.”

While Steven Taylor has already been ruled out of Monday’s game after suffering a recurrence of an ankle problem, both Mark Viduka and Obafemi Martins are expected to be fit to start against Pompey.

The duo, who were secondhalf substitutes in last weekend’s 1-0 defeat to Tottenham, will team up in attack, with Michael Owen playing in the hole behind them, a formation that mirrors the Kevin Keegan- inspired system that brought Newcastle so much success in the latter stages of last season.

Viduka’s muscularity could be crucial against a Portsmouth side likely to include imposing duo Sylvain Distin and Sol Campbell, and for all of his problems in the past, Shearer is delighted to be able to call upon the talented Australian.

“Mark’s a threat,” he said.

“He can hold the ball up, and can probably do something that no one else in our team can do at this moment in time.

“He’s a valuable asset and he could be important to us, but it’s all about keeping him fit.

“At this moment in time, we’re hopeful that he might be fit for Monday, but to be honest it’s really a case of monitoring him every day.”