Martin O’Neill’s men got off to the perfect start when Cyrus Christie’s deep free-kick was misjudged by Georgia goalkeeper Giorgi Makazridze, which allowed Shane Duffy to head home.
On 34 minutes though, Valeri Kazaishvili levelled things up at 1-1, when he latched on to Jano Ananidze’s through ball to finish from close range.
As Ireland pushed for a winner late on, Long laid on a superb pass to put James McClean through, but he couldn’t find the finish.
They are still within touching distance of their next opponents Serbia, who they meet in Dublin on Tuesday as they look to close the two point gap.
Tadić played 66 minutes of the contest at Stadion Partizana before being replaced by Adem Ljajić.
Serbia took control after 20 minutes through Eintracht Frankfurt midfielder Mijat Gaćinović, before Aleksandar Kolorov doubled the advantage before the break.
And just under ten minutes from time, Newcastle forward Aleksandar Mitrovic made sure of all three points.
Tadić could go head-to-head with Shane Long on Tuesday when the sides meet in Dublin in another crucial clash.
Manolo Gabbiadini was a late substitute for Italy as they lost 3-0 to Spain in their latest World Cup qualifier.
The hosts went in front when Isco’s free-kick from 20-yards beat Gianluigi Buffon after Leonardo Bonucci had brought down Marco Asensio.
And on 40 minutes, Isco made it 2-0 with an unstoppable drive from distance after picking up Andres Iniesta’s pass.
Spain had never lost a home World Cup qualifier, with 46 wins and nine draws, and the precious points were secure when substitute Alvaro Morata slammed home Sergio Ramos’ cross.
Gabbiadini replaced Ciro Immobile with ten minutes left in the contest, and had a chance to reduce the arrears in stoppage time but David de Gea stood up well to make a save.
Defeat means Italy are now three points adrift of Spain, with Israel next up on Tuesday 5th September (7.45pm BST).
Summer signing Hoedt is first up, as the Netherlands host Bulgaria in a match they desperately need three points from (5pm BST).
The Dutch have slipped to fourth in Group A after Thursday’s 4-0 loss away to France, with this evening’s opponents two points ahead of them, in third.
With only three games remaining, Hoedt and his teammates will be looking to overhaul Bulgaria and start reeling in Sweden and France, who are currently three and six points better off than them respectively.
Portugal are also playing catch up in Group B, although the situation for them is far less precarious.
Cédric and his teammates are in second place, three points behind leaders Switzerland – who they will host in the final group match.
They still have two more fixtures to play before then, though, beginning with tonight’s trip to Hungary (7.45pm BST).
With Switzerland visiting bottom-placed Latvia, a win might well be necessary for Portugal to keep the group leaders within striking distance.
The European champions will head into the game with confidence, having won their last six qualifiers, following their defeat away to the Swiss in their group opener.