PAUL GALLACHER has warned that Partick Thistle could be embarrassed by Celtic if they produce the same level of performance that saw them crash out of the Scottish Cup at the weekend.

The Jags turned in one of the worst showings of Alan Archibald's reign as Inverness Caley won 2-1 at Firhill to clinch a quarter-final berth.

It could have been far worse for Thistle as Caley failed to make the most of a shocking defensive display in the first half.

A Lyle Taylor strike on his return to the club was the only silver lining for Archibald, and Gallacher knows they must improve for the visit of Ronny Deila's champions on Wednesday night.

He said: "We just need to try and take the positives into the Celtic game. We need to also rectify the negatives and quickly.

"With the greatest of respect to Inverness, Celtic are a right good team going forward and, if we defend like we did in the first half, they could score a few and it could get embarrassing.

"If we don't listen to the game plan the gaffer sets out, we could be on the end of a severe loss. We need to build on the second-half performance for the game on Wednesday. You want to play against the best. That's why you want to play at the highest level.

"When Celtic come to your home ground it's fantastic. On the back of a poor performance, we need to stick to the game plan the gaffer sets out and improve because they are a fantastic outfit.

"No-one expects us to go and win the game as we're playing against a team who are fantastic going forward and are really hitting the high notes. Ronny has got them playing well, they're doing well in the cups and they've got confidence.

"It's up to us to show we are good players and we can play against the best. Celtic are the best in the country at this moment in time."

With only a handful of top-flight teams left in the competition, it was a real chance for Thistle to embark on a Scottish Cup run.

But the Jags let themselves down as they struggled at the back and created few opportunities at the other end.

Goals from Marley Watkins and Greg Tansey were enough for John Hughes' side and Gallacher was deeply disappointed with a poor performance. He said: "The first half is verging on unacceptable after the standards we've set. The second half, we took on board what the gaffer was telling us and we might have had a replay.

"The opening period was one of the worst since I've been at the club. It's not like us at all. It was poor and hard to take. We were just sitting there at half-time knowing we'd been so poor.

"The gaffer told us as much and rightly so. We did respond to a degree because there were chances."

With their cup dreams in tatters, Thistle must pick themselves up and look to get back on track and climb the Premiership standings.

The Jags are nine points off the top six and seven ahead of the relegation play-off zone, and Gallacher knows they need to address their faltering form before they get dragged into the three-way fight at the bottom of the table.

He said: "I think we've got to look behind us, to be honest, because we are so inconsistent. We need to get a few results on the board and try to progress. We experienced it last year and it's not nice to be down there.

"We saw what happened to Hibs last season. Everybody thought they were okay, but they got dragged down and paid the price.

"You don't want to be involved in a relegation battle. We need to get consistency, get a few results and hopefully be climbing up the table."