Group supremacy will be on the line in World Cup qualifying when reigning world and European champion Spain travels to play France and England goes to Montenegro in Tuesday's standout games.
The teams currently in first place were not expected to be, with France two points clear of Spain and England lagging behind Montenegro by the same margin.
''It will be a difficult match but we shouldn't have any apprehension,'' France coach Didier Deschamps said. ''We will take the battle to them.''
After Tuesday's critical games, both England and Spain could be five points adrift and facing the prospect of a playoff to reach next year's World Cup.
Elsewhere, teams like the Netherlands, Russia and Germany can already hear the Samba beats of Brazil as they hold comfortable leads in their qualifying groups.
Most teams preparing to face Spain struggle to come up with a successful game plan, but this time it's the Spanish who are uneasy after slipping to 1-1 home draw with Finland on Friday and losing the Group I lead to France, which beat Georgia 3-1.
''The squad is angry and we accept the criticism,'' Spain defender Gerard Pique said. ''But we still have margin to make it right.''
After recording 24 straight wins in qualifiers dating back to 2007, Spain has been held to consecutive 1-1 home draws and heads to Stade de France with a point to prove.
''The result is a disaster. Now we face France with everything on the line,'' Spain's all-time leading scorer David Villa said. ''We have to go to France looking to win.''
Coach Vicente del Bosque hopes to have playmaker Xavi Hernandez back from a nagging muscle problem, and Xabi Alonso returns in midfield. But he will be without attacking midfielder David Silva through suspension and left back Jordi Alba who has a thigh injury.
France drew 1-1 away to Spain last October thanks to Olivier Giroud's last-gasp headed equalizer and dominated the second half - a rare feat against the Spanish.
''Tuesday will be a completely different game,'' France midfielder Blaise Matuidi said. ''They will be even more motivated after their result against Finland.''
England warmed up for Montenegro with an 8-0 destruction of San Marino that felt like a training match as the players shared the goals. Montenegro had to fight much harder, needing a late winner from Juventus forward Mirko Vucinic to scrape a 1-0 win at Moldova.
''It would be a great lift to win on Tuesday, but if we don't get it I won't be getting the spade out to dig a grave for the team,'' England coach Roy Hodgson said. ''There are 15 points to play for and the team is capable of getting a large number of those points to see us through.''
Hodgson welcomes back midfielder Steven Gerrard and left back Ashley Cole, who were rested against San Marino, but will be without Gary Cahill and Theo Walcott due to injury. Jermain Defoe staked his claim for a starting place after scoring twice on Friday.
Ukraine and Poland are both six points behind England in Group H, with Montenegro leading the way with 13 points. Ukraine faces Moldova and Borussia Dortmund striker Robert Lewandowski will be looking forward to target practice as Poland faces San Marino.
Group A is much tighter, with Belgium and Croatia level on 13 points.
Croatia has the tougher game away to Wales - which will be relying on Gareth Bale to continue his scoring spree - while Belgium hosts struggling Macedonia. Serbia faces last-place Scotland in the other game.
Elsewhere, the Dutch and the Germans are five points clear of Hungary and Sweden, respectively, in their groups while Russia has won every match so far and are four ahead of Israel and Portugal despite playing a game less.
Germany, which has played one game more than Sweden in Group C, hosts Kazakhstan having just beaten the Kazakhs 3-0 away from home.
''I believe our task has to improve our game further and to find ourselves more as a team,'' said Germany midfielder Sami Khedira.
Germany will be without midfielders Julian Draxler (concussion) and Bastian Schweinsteiger (suspension). Striker Mario Gomez and defender Benedikt Hoewedes are nursing thigh problems but are in the squad.
Ireland is in fourth place but a win at home to Austria will move it provisionally above Sweden, which does not play.
Italy, which leads Group B by one point from Bulgaria having played a game less, goes to Malta, while Bulgaria faces a difficult match away to third-place Denmark. The Danes will move one point behind Bulgaria if they win. The fourth-place Czechs travel to Armenia.
Portugal, which is in third place and trails Israel on goal difference, needs a confidence-boosting win at Azerbaijan after Friday's surprise 3-3 draw away to the Israelis, who travel to Northern Ireland in the other Group F match.
The Dutch will be looking for a sixth straight win in Group D against visiting Romania, while second-place Hungary - level on points with Romania - goes to fourth-place Turkey. In the other match, Andorra hopes to both avoid a sixth straight defeat and score its first goal when it travels to Estonia.
