Eight teams remain for four spots in Russia.
[ MORE: MLS Conference Finalists cheat sheet ]
There are some big names in the bunch, including multiple World Cup winners like Italy.
And five of the eight teams advanced from their groups at EURO 2016, including quarterfinalist Italy.
Italy is also one of four playoff teams who went to the 2014 World Cup. Not all will go back, with Greece facing Croatia in one of the playoff ties.
Northern Ireland vs. Switzerland
First leg - Thursday in Belfast
Second leg - Sunday in Basel
The Swiss were incredibly unfortunate, going 9-1 just like group-winning Portugal but failing to advance on goal differential.
The plucky Northern Irish proved their EURO run was no fluke when they advanced fairly comfortably over third place Czech Republic.
Switzerland will be favored to advance behind its terrific midfield, with Stoke City’s Xherdan Shaqiri, Arsenal’s Granit Xhaka, and the Montreal Impact’s Blerim Dzemaili in the mix.
Northern Ireland will line up in from of EURO hero Michael McGovern, who starred in helping the Green and White Army stymy several foes in 2016.
Croatia vs. Greece
First leg - Thursday in Zagreb
Second leg - Sunday in Piraeus
Croatia comes out of a wildly competitive Group I, two points behind Iceland and three points ahead of Ukraine.
Greece needed the final day to edge past Bosnia and Herzegovina after finishing miles behind Belgium.
Croatia is loaded in attack and style, but Greece has traditionally been a squad full of tactically-efficient defenders.
Denmark vs. Republic of Ireland
First leg - Saturday in Copenhagen
Second leg - Tuesday in Dublin
The Danes finished five points back of Poland and four ahead of Montenegro in Group E.
Ireland edged Wales for second place in Group D.
Expect this pairing to be as plucky as any of the four ties, with Martin O’Neill’s Irish prepared to make life very difficult for unbeaten-since-Oct. 2016 Denmark.
Sweden vs. Italy
First leg - Friday in Solna
Second leg - Monday in Milan
The Italians lost the Group G lottery, which was always going to come down to the pair of matches between Italy and Spain.
Sweden advanced past Netherlands on goal differential for second in Group A, finishing four points behind France.
Since 1934, Italy has failed to qualify for a World Cup exactly once (1958). Sweden didn’t make it to the last two tournaments despite a certain Zlatan Ibrahimovic. There would be a certain ridiculousness to the Swedes making it happen without one of their all-time heroes.
