ADAM MATTHEWS was unable to prevent Celtic slipping to defeat against Dundee United.

And the Hoops full-back believes it is proof Ronny Deila's men have a title fight on their hands.

The Parkhead club currently sit four points clear at the top of the SPFL Premiership table, with United and Aberdeen four points behind.

In fact there are four teams within striking distance as the season reaches its halfway point.

Tannadice boss Jackie McNamara went to great lengths after their 2-1 victory on Sunday to dismiss claims anyone can challenge Celtic for the league title this year.

However, it's not an opinion shared by Matthews.

The Welsh international said: "I think the league this year is strong. Aberdeen, Hamilton and Inverness have done well, so we know it's going to be tough. But we're where we want to be at the minute.

"I think we wanted a bigger gap, especially with the game in hand on Sunday. But we've got to focus on one game at a time and hopefully get the win next game."

"I think other teams are just playing it down. If they're close to us they're going to want to make a title race of it.

"We know that the pressure is on us and we're expected to run away with it, but it's not going to happen like that in football.

"Every time someone plays Celtic they step up their game. We knew it was going to be tough at the start of the season."

He added: "I think this season has proved that. When we're not on our game we get beaten.

"That's why the gap's four points and people are within touching distance. We go into every game with the same mindset.

"As I said, on Sunday we played all right, had a few chances and didn't take them."

One man who did make the most of the opportunity afforded to him was Leigh Griffiths.

The striker burst into life when he came off the bench on Sunday, netting a goal before striking the post in the dying seconds.

But despite finding it difficult to find a run of games under Deila, Matthews said of his team-mate: "He's looking good in training and he's a goalscorer.

"When he plays you've got a good chance and nine times out of ten he will put it away. He took his goal really well on Sunday and he was unlucky with the one that hit the post.

"He's training really well but obviously we've got a lot of good strikers with Guidetti, Scepovic and Griff. They're all training well."