Chris Burke's penalty gave Kilmarnock a deserved 1-1 draw with Celtic, as the champions dropped points in only the second game of the season.
Neil Lennon's team got off to the perfect start at Rugby Park, taking an 11th-minute lead when stand-in Kilmarnock goalkeeper Danny Rogers was beaten cheaply by Ryan Christie's long-range free-kick.
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But with Christopher Jullien struggling to deal with Kilmarnock's physical forward play all afternoon, he hauled down Nicke Kabamba in the Celtic box allowing Burke to step up from 12 yards and level up from the spot (24).
Kilmarnock: Rogers (7), Millen (7), Broadfoot (8), Findlay (8), Waters (6), Power (7), Dicker (7), Tshibola (7), McKenzie (6), Burke (7), Kabamba (8).
Subs: Haunstrup (6), Kiltie (n/a).
Celtic: Barkas (7), Frimpong (6), Jullien (4), Ajer (6), Taylor (6), Brown (5), McGregor (6), Forrest (6), Christie (7), Elyounoussi (5), Edouard (5).
Subs: Kimala (6), Elhamed (5), Ntcham (n/a), Bolingoli (n/a).
Man of the match: Nicke Kabamba
After the break, Celtic enjoyed near-total dominance of the ball but did not once force Rogers into a difficult save, as Kilmarnock's stubborn defending led them to a well-earned draw for their first points of the season.
Kilmarnock show grit to hold champions
After last weekend's thumping win over Hamilton, while Kilmarnock were getting beaten at Hibernian, it would have been no surprise if Celtic flew out of the blocks at Rugby Park - but against a well-drilled and physical Killie side, they found life tough.
It had been the hosts making the early ground, as Kabamba caught out Jullien and broke with less than two minutes on the clock before Kristoffer Ajer bailed out his defensive partner.
But with their first sight of goal, Celtic showed their clinical touch. Back-up goalkeeper Rogers should have done better with Christie's 35-yard free-kick, which he was late to dive for and could only watch it sail past him.
But 11 minutes later, his blushes were spared. Kabamba again gave Jullien problems, this time on the byline in the Celtic box, and was then hauled down by the Frenchman.
Kilmarnock made two changes from their defeat at Hamilton, with Danny Rogers replacing injured goalkeeper Jake Eastwood, and Gary Dicker taking Greg Kiltie's place in midfield.
Celtic's only alteration also came in goal, with Scott Bain dropped for debutant Vasilis Barkas.
There was little surprise when a penalty followed, and even less so when Burke beat Celtic debutant Vasilis Barkas with an excellently taken spot-kick.
Celtic continued to give Killie right-back Ross Millen too much space to send in fine deliveries from the flank, with Kabamba nodding two crosses over Barkas' bar, while Odsonne Edouard fired a free-kick just wide of Rogers' post from 20 yards.
After the break, the champions showed signs of increasing their intensity and tempo, but it did not last. After Edouard fired over from outside the box, they did not come close to testing Rogers again until Callum McGregor's long-range effort whistled over the bar nearly 20 minutes later.
Kilmarnock showed glimpses of danger on the counter-attack without ever providing Barkas any major worries on his Celtic bow, but held on resolutely for a first point of the season, and leave Celtic frustrated and already off the early pace-setters.
What the managers said...
Kilmarnock manager Alex Dyer: "We had to put in a disciplined performance, and after going a goal down, we lost it after they scored for a few minutes, but then we were back in the game with the penalty and saw the game out quite comfortably.
"These boys have been here before, they know what it's about, they showed good discipline, and I know the players I've got in there, the way they work, that we could get over that initial 10 minutes after the goal and after that we were fine.
"We said at half-time, stay in the game, that was our motto for the last few seasons, it gives ourselves a chance."
Celtic boss Neil Lennon: "We're disappointed not to win the game. We had enough of the ball, we've given away a poor goal, but we've dominated the second half, and just lacked a bit of penetration.
"Kilmarnock defended very, very well at times as well though. We never scored from open play, we scored a great goal from a free-kick, but let them back into the game and gave them oxygen.
"Second half was all us, but we just lacked that bit of quality on the day. We've dropped two points, if you want to look at it that way, but it could be an important point going forward, this is a tough place to come."
Man of the match - Nicke Kabamba
Kilmarnock knew Celtic's defensive weak spot and took full advantage of it. Kabamba took on more duels than anyone on the pitch - more than double, in fact (31). While he won just under half, he was a constant annoyance for Jullien and Ajer and regularly got the better of them.
He will wish his finishing could have been slightly better from two good Millen crosses before the break, but he more than played his part in Burke's equaliser by winning the penalty his team-mate tucked away in a performance of real effort and quality.
"He was excellent from start to finish," his manager Dyer told Sky Sports after the game. "He ran the two boys who are good players ragged at times, no one likes to defend when balls are being turned, but he's big, he's strong, he's got a great touch and he's a handful for any defender in this division."
Kilmarnock travel to Ross County on Wednesday; Kick-off at 7.45pm, before hosting St Johnstone next weekend.
Celtic have another away trip to St Mirren next up, live on Sky Sports Football on Wednesday from 5pm; Kick-off at 6pm.