By any measure, Brazil and Spain are considered the two best teams in the world right now. They are the two betting favorites to win the World Cup. Brazil is No. 1 and Spain is No. 2 in ESPN's Soccer Power Index, while the two are flipped in the FIFA World Rankings.

As the rankings imply, each has also been in fine form since the 2006 World Cup. Brazil won the 2007 Copa América, while Spain won the 2008 European Championship. Their recent continental successes would seem to indicate good things for each country in South Africa. But does history agree?

First, let's take a cursory look at the four continents that have never won a World Cup. As expected, the reigning champions from CONCACAF, Africa, Asia and Oceania have had negligible success at the World Cup. The only team to even reach the quarterfinals was the United States in 2002. In this regard, don't expect a deep run from Oceania champion New Zealand or 2009 Gold Cup winner Mexico. 2007 Asian champion Iraq and 2010 Africa Cup of Nations winner Egypt didn't even qualify for South Africa.

All 18 World Cup winners have come from South America and Europe, so the winners of Copa América and the European Championship would logically be expected to have had significantly more success.

Since Copa América was first held in 1916, the triumvirate of Argentina, Uruguay and Brazil has dominated, winning 36 of 42 titles. Since the World Cup began in 1930, those three countries have won nine of the 18 tournaments. Shockingly, however, no reigning South American champion has ever won the following World Cup.

Copa América winners have reached the World Cup 13 of 18 times. Excluding 2007 Brazil, of course, eight of the remaining 12 teams advanced past the group stage, including Peru's trip to the second group stage in the uniquely formatted 1978 tournament. Four countries made the semifinals, and three finished runner-up: 1930 Argentina, 1950 Brazil and 1998 Brazil. Coincidentally, 1930 Argentina and 1950 Brazil each lost to fellow CONMEBOL member Uruguay in the final. These numbers indicate that Brazil is likely to advance from the Group of Death in South Africa, and has a good shot to reach the semifinals. Not that stats were necessary to figure that out. However, if Brazil wins the title, the five-time champions would set yet another historical precedent.

Reigning Copa América Champions at Next World Cup
Possible teams: 18*
Qualified: 13*
Round of 16: 8
Semifinals: 4
Champion: 0

* Includes 2007 Brazil

Moving to the continent that has hosted 10 World Cups, the European Championship was first played in 1960 and has been held two years before the World Cup ever since. Of the 13 Euro winners, 10 have proceeded to qualify for the next World Cup. Only 1976 Czechoslovakia, 1992 Denmark and 2004 Greece did not reach the grand stage. Six of those 10 emerged from the group stage, and the last five all advanced at least one round in the knockout stage. But only one country managed to parlay its European title into a World Cup title, when West Germany won on home soil in 1974. History again indicates about what is expected: Spain is likely to advance, with an above-average chance to reach the semis. However, the odds of a championship are slim.

Reigning European Champions at Next World Cup
Possible teams: 13*
Qualified: 10*
Quarterfinals: 6
Semifinals: 4
Champion: 1

*Includes 2008 Spain

In sum, of the 21 reigning champions of South America or Europe, the only one to win the following World Cup was West Germany, which did so as host of the 1974 World Cup. This lack of repeated success can be attributed to a wide range of reasons, from the varied importance a country places on a competition to coaching changes to injuries to simple bad luck. Regardless, this is not a good omen for the ultimate success of Brazil or Spain.

Trying to find a pattern from the opposite direction, 14 of 18 World Cup champions participated in the most recent continental championship during the four-year World Cup cycle. Ten of those 14 finished in the top eight, and seven of the 14 reached at least the semifinals.

World Cup Champions at Previous Continental Championship
Participated: 14
Top eight: 10
Semifinals: 7
Champion: 1

Looking backward provides slightly more correlation to success, which is a good omen for Euro 2008 champion Spain and runner-up Germany, although semifinalists Turkey and Russia did not qualify. All four 2007 Copa América semifinalists will be in South Africa. Brazil won the title 3-0 over Argentina, and invitee Mexico defeated Uruguay 3-1 for third place.

The bottom line is that winning two straight major soccer tournaments over a multiyear stretch is extremely difficult, regardless of skill or talent. Let this be a warning to anyone expecting or hoping for Brazil and Spain to roll to the final in Johannesburg.

Paul Carr is a researcher for the ESPN Stats & Information group.