Lineen saw his side win 41-31 against the Italian underdogs at Firhill but then admitted he was far from happy.

The coach declared: 'I have absolutely nothing good to say about the game or our performance, apart from the fact that we picked up five points.

'I won't blame anyone in particular. It was just a dreadful day at the office.

'Viadana showed a lot of guts and they took their chances well. But from my point of view it was definitely the poorest display I have seen from Glasgow since I became involved with the club.

'We have a huge amount of work to do if we want to have any chance of being involved in the battle for qualification to the knock-out stages.

'First, we have a massively important league match against Cardiff next weekend and we will have to improve considerably.'

Calvin Howarth gave his former Glasgow team-mates an early wake-up call as the visitors raced into a shock lead.

His clearance was not pounced on by Bernie Stortoni and winger Hayden Pedersen scooped up the loose ball and cruised in for a try under the crossbar, handing Howarth a formality of a conversion.

The Warriors scored a try through Hefin O'Hare and Dan Parks slotted the extra points before banging over a 40-metre penalty awarded for offside.

Glasgow recorded a quickfire burst of scores by Parks and recalled centre Graeme Morrison.

Parks goaled them both to open up a 17-point gap midway through the half but Viadana got the next score through Pedersen, with Howarth converting before missing a penalty.

He rediscovered his touch two minutes after the restart with a well-struck angled effort from 40 metres.

Aldo Birchall then pounced for Viadana's third try following a quickly-taken tapped penalty. Howarth's kick tied the contest.

The Italians were reduced to 13 when Birchall and Dion Waller were yellow-carded.

Substitute scrum-half Sam Pinder darted over from close quarters for the all-important fourth score.

And at last they made their experience count with a try by John Barclay with Parks taking his personal tally to 21 points.

But the Italians had the last word with a chip-and-chase counter from Steven Bortolussi, converted by Howarth.