Five World Cup story lines

1) Who's better: Portugal's Cristiano Ronaldo or Argentina's Lionel Messi?

That's a debate for the ages, and this year's World Cup could add fuel on either side of the argument. Neither has held soccer's biggest prize, and this summer's tournament could be the last chance at capturing a World Cup title for both: Ronaldo will be 37 when the next World Cup kicks off in Qatar while Messi, his longtime rival in Spain's La Liga, will be 35. Messi came close in 2014, with Argentina falling to Germany 1-0 in the final.

They are among a number of stars to watch in this year's World Cup, a list that also includes Neymar (Brazil), Mohamed Salah (Egypt), David de Gea (Spain), Eden Hazard (Belgium), Antoine Griezmann (France), James Rodriguez (Colombia), Thomas Mueller (Germany) and Gabriel Jesus (Brazil).

2) In the group stage, the top two teams advance to knockout play. The top team from Group A plays the second-place team in Group B, and the second-place team in A plays the top team in B. Groups C-D, E-F, and G-H work the same way. According to simulations of possible outcomes run by Gracenote, here is the percent chance each team in each group will advance to the knockout stage. (In each case, the numbers add up to 200 because two teams from each group make it).

• Group A: Uruguay (77 percent), Russia (60), Egypt (36), Saudi Arabia (27)

• Group B: Spain (76), Portugal (58), Iran (35), Morocco (30).

• Group C: France (69), Peru (68). Denmark (35), Australia (27).

• Group E: Brazil (90), Switzerland (51), Costa Rica (31), Serbia (28).

• Group F: Germany (79), Mexico (60), Sweden (34), South Korea (27).

• Group G: England (71), Belgium (71), Tunisia (32), Panama (26).

• Group H: Colombia (77), Poland (50), Senegal (45), Japan (29).

3) Group A seems to be the easiest of the groups, with Russia and Saudi Arabia — the two teams with the lowest FIFA rankings of all 32 teams at the World Cup — are in that group. You'll note that host Russia still has a favorable chance of advancing. Several groups can lay claim to the "Group of Death" moniker typically bestowed on the toughest group, but there doesn't seem to be a consensus. Maybe there really isn't a Group of Death this year?

Cost rises, worker deaths and corruption have marred the building of Russia's World Cup stadiums. Unlike in Brazil four years ago, venues were finished on time, but there's sure to be a few last-minute tweaks ahead of the tournament. Legacy is an issue; only five stadiums hosted top-level clubs this season, and the government will need to cover the upkeep with subsidies after the tournament.

5) In a country better known for its baseball players and boxing champions, soccer will muscle into their territory when Panama makes its first trip to the World Cup. The Central Americans aren't complete unknowns. Twice runners-up at the CONCACAF Gold Cup, they qualified for the tournament in Russia by finishing ahead of the United States. That's despite the huge disparity between the countries: Panama has only 4 million people, while the U.S. has about 320 million.

Associated Press, Washington Post