Get out the calculators. It's number-crunching time for Argentina and six other South American countries still vying for places in next year's World Cup in Russia.
Argentina is in danger of missing its first World Cup since 1970 - almost a half-century ago.
This would mean no Lionel Messi to drive television ratings; no Messi to spur ticket sales for local organizers; no Messi to distract from off-field controversies surrounding the world-governing body, FIFA.
The top four teams in South America advance automatically, and the fifth-place team has the chance to advance from a playoff next month against New Zealand, the representative of Oceania.
Brazil has already qualified with 38 points. Uruguay is next with 28 and is widely expected to qualify. That leaves five teams with varying prospects: Chile (26), Colombia (26), Peru (25), Argentina (25), and Paraguay (24).
Tuesday's matches will all start at the same time: Ecuador-Argentina, Brazil-Chile, Peru-Colombia, Paraguay-Venezuela, and Uruguay-Bolivia.
Here's a quick look at the chances and the qualifying rules.
If teams are tied on points, the tie-breakers in order are: overall goal difference; overall goals scored; points in matches between tied teams; goal difference in matches between tied teams; goals scored in matches between tied teams; away goals scored in matches between tied teams; "fair play points" based on yellow and red cards.
And if that won't solve it, get set for the drawing of lots.
Argentina has scored only one goal in its last four matches. Coach Jorge Sampaoli has excluded team veteran Gonzalo Higuain and has tried all kinds of forward combinations with Messi: Paulo Dybala, Mauro Icardi, Dario Benedetto, and Alejandro Gomez.
Nothing has worked so far.
Argentina faces Ecuador in the thin air of Quito, located at 2,850 meters (9,350 feet) in the Andes - always a trial for visiting teams.
There is some good news for Argentina: it has fate in its own hands.
If it wins, it is guaranteed at least a playoff with New Zealand, and that result might also yield an automatic berth. Even a draw could get an automatic berth - but only if Colombia beats Peru, Paraguay fails to beat Venezuela, and Chile loses to Brazil by at least two goals. A draw could also yield a playoff for Argentina.
A loss even leaves the door slightly ajar for a playoff spot. For that to happen, Paraguay must fail to beat Venezuela, and Peru must lose to Colombia by a larger margin than the margin of Argentina's loss.
Uruguay is already assured of at least a playoff though, in reality, it's virtually a cinch for a top-four finish. The only way for Uruguay to fall to fifth is: it loses to Bolivia, plus Chile, Colombia and Argentina all win - and Argentina scores at least nine goals to overtake Uruguay on goal difference.
A victory guarantees Chile - the two-time defending South American champions - its third straight World Cup berth. A draw would also be enough to get an automatic spot if Peru and Colombia draw, and Argentina fails to beat Ecuador. A draw would be good enough for a playoff spot if Argentina wins, and there is a winner in the Peru-Colombia match.
Chile can also reach an automatic berth, or a playoff, with a loss. But every contingency must fall right.
Colombia gets an automatic berth with a victory at Peru - regardless of other results. A draw would also be good enough if Argentina wins, or Chile loses in Brazil. A loss might also be enough for a playoff, but this would require other results to fall in Colombia's favor.
Peru can qualify for its first World Cup since 1982 if it wins at home against Colombia, unless Chile beats Brazil, and Argentina beats Ecuador by a margin greater than Peru's margin over Colombia.
A victory would guarantee Peru at least a playoff. A draw and even a loss could be enough for a playoff spot, depending on other results.
Paraguay needs the most help. It must win against Venezuela to have any chance at the playoffs. It will be out with a draw or a loss.