Glasgow Warriors might have breathed a sigh of relief when Zebre full-back Daniel Halangahu wafted a 75th-minute penalty effort wide, but they could take little comfort from the moment that preceded it, as Moray Low suffered what looked like a serious knee injury when he took a heavy blow in a ruck.

The prop was carried off after lengthy treatment on the pitch, but Scotland are now looking at a tight-head crisis as their autumn Test series looms.

If, as seemed likely last night, Low is out of action for an extended period, then Geoff Cross could be the the only tighthead available for the match against the All Blacks on November 11. Low's Glasgow team-mates Ed Kalman and Jon Welsh are both also on the injury list at the moment, while Euan Murray is ruled out by his refusal to play on Sundays.

Such issues may no longer be Gregor Townsend's concern, but the Glasgow coach was not exactly full of the joys at the end of a game his side had begun by coughing up 13 early points. "We got the win and that's what we're here for, but it was our poorest performance of the season," he said.

"We did not look on the game early in the match. We were inaccurate, missing tackles and losing ball. But after that I was very pleased to come back and show resilience and resolve to come back and score tries."

Glasgow took a lot of experience out of the side that had won their previous two games by fielding four debutants and a host of peripheral players in the starting line-up, but they also seemed determined to dynamite some first principles of rugby with early tactics that were as bold as the selection.

Rather than take control of proceedings through the forwards, they tried to move the ball wide in the opening stages – with the almost inevitable consequence that they turned the thing over with galling regularity. For the home fans, it made grim viewing to watch their side concede two quick penalties and fall 6-0 down in the first 10 minutes, but it threatened to become a horror show when the Italians won a ruck on the Warriors' line and Zebre fly-half Luciano Orquera danced through the misaligned defence for a comically soft try.

Graeme Morrison could be seen reading the riot act beneath the posts even as Orquera made the conversion, and the immediate consequence was that Glasgow began to play on a narrower front. At last, they began to make significant progress, although it was a passage of broken play and an error by Zebre full-back that allowed lock Tim Swinson to chase his own hacked kick ahead and dive over for Glasgow's first points.

In fairness, Glasgow had been frustrated by some pretty cynical spoiling by the Zebre forwards, but the Italians paid a hefty price when referee Leighton Hughes punished their negativity with two yellow cards in the space of four minutes. That should have brought a Glasgow onslaught; instead, the next event on the scoreboard was the recording of three more points for another Zebre penalty.

At half-time Glasgow held a 19-16 advantage, though, and it would be hard to argue that it was not deserved by then. DTH Van der Merwe dived over acrobatically, and cleverly, for a try in the left corner after a neat pass from Josh Strauss, and the Canadian wing was instrumental in Graeme Morrison's touchdown just before the interval, although he pulled up with what looked like a hamstring problem even as he offloaded the scoring pass.

Van der Merwe's misfortune brought Stuart Hogg into the fray at the start of the second half for his first appearance of the season. His arrival brought a lusty roar from the crowd, but again it fell to Zebre to harvest the next points as Orquera, a man whose goal-kicking routine has all the urgency of a tectonic plate, clipped over another penalty to draw the sides level.

Orquera was not alone in the Zebre ranks when it came to wasting time, but their blatant attempts to wind down the clock did at least wind up the Glasgow crowd. So, too, did the more direct approach of the Warriors, who virtually took up residence in their opponents 22. However, Glasgow failed to come away with points and their frustration was compounded when Ruaridh Jackson, who kicked poorly throughout, sent another penalty effort wide just after the hour mark.

Jackson was replaced by Peter Horne soon afterwards. At the same time, Ryan Wilson took over from Strauss, who had seemed a little off the pace throughout. Within a few minutes, Glasgow won a scrum in front of the posts, Zebre drove too early, and Horne shot the resultant penalty over. Not the prettiest way to clinch a game, but then the rest of the match had hardly been a thing of much beauty either.