Celtic missed out on a valuable Europa League win after conceding a late penalty to allow Udinese a share of the points in Glasgow.
Ki Sung-Yueng put Celtic ahead from the spot, when Gary Hooper was fouled inside the box after just two minutes.
But 83 goalless minutes later Hooper was judged to have fouled Brazilian Neuton inside the box with Almen Abdi slotting home the resultant penalty.
The outcome leaves Celtic bottom of Group I on goal difference.
Manager Neil Lennon had made significant changes to his line-up: with goalkeeper Lukasz Zaluska back in favour having not played since the signing of Fraser Forster in the August transfer window.
Glenn Loovens and Anthony Stokes were also dropped in favour of Victor Wanyama and Mohamed Bangura, who made his first start.
Within two minutes Hooper found his way into the opposition box, only to be fouled by Joel Ekstrand - the additional assistant behind the goal appearing to confirm the award of a penalty.
The resulting spot-kick was taken by Ki, the Korean coolly executing a perfect strike into the top left hand corner to give Udinese keeper Samir Handanovic no chance.
Having travelled with a weakened squad and without talismanic striker Antonio Di Natale, the Italians appeared to struggle with Celtic's early pace: Zaluska untroubled in the opening 20 minutes of his return to first team action.
The Poland international was called into action in the 22nd minute to deal with a long-range shot from midfielder Emmanuel Badu which he pushed round the post. Midfielder Almen Abdi also forced a save with a shot from 18 yards out six minutes later.
But Hooper delivered an instant reply: finding himself in space 25 yards out and powering a shot towards the Udinese goal, Handanovic forced to parry the ball away to keep the deficit at a single goal.
And despite the inexperience of a team with seven players aged 23 or under, the Italian side held on until the break: Ki closest to extending Celtic lead with a free kick 20 yards out in the 37th minute which he sent wide.
Joe Ledley failed to emerge for the second half and was replaced by Mark Wilson who was forced to adapt to a game still being played at blistering pace.
Celtic looked in no real danger of losing their lead until in the 62nd minute Medhi Benatia had the ball in the net from Cristian Battochio's chipped free-kick 30 yards but amid more confusion referee Bulent Yildirim consulted his lineman and ruled that Benatia was offside.
The home side increased their attacking options with the introduction of Georgios Samaras and there were late chances for Ki at one end and Mauricio Isla at the other, who forced a tremendous save from Zaluska with six minutes remaining.
But Celtic's undoing was to be beyond the keeper's control, Hooper appearing to body-check Udinese defender Neuton inside the box with Lennon's side just minutes from victory. On this occasion the referee Yildirim had no hesistation in pointing to the post, with Abdi slotting the ball into the net to level the tie.
Celtic had an opportunity to rescue the game in the dying seconds when Samaras was fouled just outside the box, but Mulgrew's left-footed effort was parried clear to end the Glasgow side's hopes of a first win in Europe this season.