Scotland and Wales struggle after two matches in Group A
The top three seeds remain in control of Europe's 2014 World Cup qualifying Group A after the second round of fixtures.
The group was predicted to be an open affair, with all six teams capable of taking points of each other.
However, top seeds Croatia, Balkan neighbours Serbia and star-studded Belgium all sit on four points after two matches in the group.
Scotland lie two points further behind, and Wales, who prop up the table, are still looking for their first point.
Craig Levein's Scotland were booed off the park after struggling to a 1-1 draw with Macedonia , following on from a goalless encounter with Serbia on Saturday.
The Macedonians stunned Hampden Park when they took the lead after only 11 minutes through an offside-looking Nikolce Noveski.
Kenny Miller managed a leveller for the home side just before the break, but the hosts were struggling to dominate the game.
And the Balkan side looked the more likely as the match wore on, hitting the post and forcing Scotland goalkeeper Allan McGregor to make some good saves.
The result leaves Scotland with an uphill struggle to qualify for Brazil with only two points form two home fixtures.
Despite appearing to lack a cutting edge up front against Scotland on Saturday, Serbia stepped up a gear at home to Wales to record a devastating 6-1 victory .
The Serbs, who had no player in their ranks with more than eight international goals, were two goals ahead after 25 minutes through Aleksandar Kolarov and Zoran Tosic.
Thoughts of a Welsh resurgence were briefly stirred by Gareth Bale's stunning free-kick before Filip Djuricic took advantage of more poor Welsh defending to restore Serbia's two-goal advantage.
Dusan Tadic tapped in a fourth after Bale gave the ball away and Branislav Ivanovic dispossessed Darcy Blake to make it five, with Ajax's Miralem Sulejmani rounding off the scoring.
It is a result which has left Wales manager Chris Coleman 'embarrassed' by his side's defending , and Wales again looking like missing out on qualification for a major tournament.
In the other group match, Croatia held Belgium to a 1-1 draw in Brussels.
Ivan Perisic gave the visitors an early lead, but the Belgians equalised through defender Guillaume Gillet in first-half injury time.
The Belgians will probably be disappointed not to have picked up all three points however, with Zenit St Petersburg's £32m midfielder Axel Witsel guilty of missing chances.
The result leaves both teams locked with Serbia on four points, although the Serbs have a superior goal difference.
In the next round of fixtures Scotland travel to Wales, where Scotland have suffered defeats on their last two visits, for a match which has assumed vital proprtions for both nations.
Another draw is possible as Belgium travel to Serbia.
Croatia, who face Macedonia in Skopje, will be looking to take advantage and go clear at the top of the group, but, as Scotland know only too well, Macedonia are not to be underestimated.