Stefan Scepovic scored his first goal for Celtic as the Hoops made hard work of beating Astra Giurgiu 2-1 in their Europa League clash at Parkhead.
After taking four points from their first two Group D matches against Salzburg and Dinamo Zagreb, and beating Ross County 5-0 away in the Premiership on Saturday, the home side were looking to dominate the section in the double-header against a team considered the whipping boys of the group after two defeats.
However, Ronny Deila's side were out of sorts for most of the game in which Hoops goalkeeper Craig Gordon played his part again.
Serbian striker Scepovic, 24, signed from Sporting Gijon for a reported £2.3million in the summer but only playing because John Guidetti once again had to drop out as he was not registered in time for the group stages of the competition following his loan move from Manchester City, missed two sitters with early in the second-half.
But he made up for his hitherto hapless performance when he headed in an Anthony Stokes free-kick in the 73rd minute before midfielder Stefan Johansen made it 2-0, only for Gabriel Enache to pull a goal back to ensure a nervy ending.
Celtic fly to Romania for the return game on November 6 and they will have to improve on this disjointed performance if they are, on the night, to get to the 10-point mark Deila believes will ensure qualification into the knockout stages.
Celtic Park has often rocked on big European nights in the past while bursting out of its 60,000-capacity but once again the top tier of the stadium was left unopened, a tangible indication of interest among the home fans while there was no away support worthy of the term.
The home side soon had control however, and unmarked midfielder Charlie Mulgrew headed an early Anthony Stokes corner high over the bar when he ought to have hit the target.
Astra, with skipper Constantin Budescu playing the role of lone striker to the point of isolation at times, looked limited to say the least.
Celtic's corner count slowly mounted but to no avail and they seemed taken aback when, out of the blue, Astra shook off their self-imposed shackles and threatened.
In the 20th minute Gordon, in unconventional style, chested away a long-range drive from Seidu Yahaya before stopping a drive from Budescu with his foot.
Moments later, Astra's Japanese midfielder Takayuki Seto curled a low drive wide of the far post to the sound of grumbling from the stands.
The Scottish champions had lapsed into a stupor which had hamstrung their Champions League hopes.
Right-back Mikael Lustig's deep cross was almost put into his own net by Vassilis Pliatsikas but another corner was squandered before the increasingly confident visitors broke again and this time Enache drove wide of the target from the edge of the box.
In the 37th minute Scepovic headed another deep cross from Lustig over the bar from six yards.
The Serb then laid the ball on a plate for Stokes but his goal-bound shot from 10 yards was blocked by defender Cristian Oros and the home support appeared to have become as lethargic as their team, hardly able to bring themselves to boo when referee Kristinn Jakobsson blew for half-time.
When Scepovic headed Emilio Izaguirre's cross past the far post from six yards in the 51st minute before missing a similar chance moments later, this time from a Lustig cross, it looked ominous for the Hoops.
Callum McGregor was replaced by Aleksandar Tonev who soon sent a long-distance drive flashing past the post, in the absence of option and real inspiration.
In the 65th minute Astra defender Syam Ben Youssef headed a cross from Seto over the bar from eight yards, which was the cue for winger Mubarak Wakaso to replace Mulgrew.
Gordon made another save, this time from Enache, as the home side's play deteriorated further.
However, all was forgiven when Scepovic atoned for his earlier misses by heading Stokes' free-kick in off the underside of the crossbar to the relief of the Hoops fans, who began top enjoy themselves when Johansen pounced on a spilled ball by Astra keeper Silviu Lung to blast the ball high into the net.
However, when Enache nipped in at the near-post to flick the ball past Gordon following a pass from William Amorim, it was game on again.
But there was no real panic occasions in the Hoops box and indeed Scepovic went close again trying to convert Wakaso's cross, his effort blocked.