World Cup 2018 Odds for Cristiano Ronaldo's Portugal and More Sleeper Teams

The FIFA World Cup is typically dominated by a close-knit group of perennial favourites, such as Germany, Brazil and Argentina.

On football's biggest stage, the winner rarely, if ever, tends to come from left field. But there are often teams that can surprise with an impressive run.

Costa Rica topped a group containing Uruguay, Italy and England to reach the quarter-final stage of the 2014 World Cup. In that same tournament, a less-than-vintage Netherlands team finished third; reigning champions Spain were out in the group stage.

With that in mind, here's a look at some of the sleeper teams hoping to cause an upset in Russia, with odds courtesy of OddsShark.

Portugal 25-1 to Win the World Cup

It seems strange for the reigning European champions to be such long odds to win the World Cup, but Portugal are somewhat classed as outsiders heading in as the eighth favourites.

It's likely because, despite the presence of Cristiano Ronaldo, their team is relatively short on quality when compared with the squads boasted by Brazil, Germany or Spain.

Indeed, that was apparent at the last World Cup as they failed to reach the knockout phase; however, they faced a difficult group containing Germany, the United States and Ghana.

Portuguese football writer Jan Hagen is pleased with their current lineup, though:

They face Spain this time around, so claiming top spot in Group B will be difficult, but they should have little trouble escaping it given their other opponents are Iran and Morocco.

If they do come second to La Roja, they will most likely get Uruguay in the round of 16 and likely France in the quarter-final. They could not face Brazil until the semi-final and the likes of Spain, Argentina and Germany until the final.

That's by no means an easy run, and Portugal will have to punch above their weight more than once if they're to lift the trophy. However, Ronaldo has proved time and again in the UEFA Champions League that he can be a difference-maker in knockout matches.

The 33-year-old will be key to their chances. If he lives up to his billing, Portugal have a chance of beating anyone. If he struggles, they'll be unlikely to get too far beyond the group.

Senegal 5-1 to win Group H

While there is no obvious Group of Death at this year's World Cup, Group H will be one of the most difficult to navigate. All four teams—Poland, Colombia, Senegal and Japan—are capable of putting the results together to get through and can realistically hope to do so.

Topping it won't be easy, but Senegal may not be a bad choice at 5-1.

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Everton's Idrissa Gueye and West Ham United's Cheikhou Kouyate will provide an energetic and robust platform in midfield, and the Lions of Teranga will have star quality in front and behind the pair.

Napoli defender Kalidou Koulibaly will be their rock at the back. He just helped the Partenopei rack up 91 points this season, and Gianluca Di Marzio's David Amoyal has given him high praise:

Sadio Mane of Liverpool is set to star in their attacking lineup. He's had an outstanding season at Anfield, racking up 19 goals and nine assists in all competitions, and he may have won the UEFA Champions League by then, as the Reds play in the Champions League final on Saturday against Ronaldo's Real Madrid.

As football writer Joel Rabinowitz noted, Mane perhaps goes slightly under the radar at Liverpool because of his sensational team-mates:

He'll be the key man for Senegal, though, who will be looking for him to fire them through along with Moussa Sow and Keita Balde Diao.

Colombia and Poland will be particularly difficult to get past, but a win against one of the pair and another against Japan would likely see them into the knockout stage and perhaps even top the group.

Serbia 7-1 to Beat Brazil

While it may be easy to write off Serbia in this match—as it will many of Brazil's opponents—they have the talent in their side to cause more illustrious outfits problems.

Manchester United star Nemanja Matic will likely be present in midfield, alongside Lazio sensation Sergej Milinkovic-Savic. All eyes will be on the latter after he bagged 14 goals and nine assists in all competitions this season.

The 23-year-old is a box-to-box midfielder who excels at driving the side forward before creating or taking chances in the final third. He's also robust in carrying out his defensive duties, so it will be fascinating to see how he gets on against the likes of Brazil's Casemiro.

Up front, Aleksandar Mitrovic should provide much of the threat. The Newcastle United man is in red-hot form, having contributed 12 goals and an assist in 19 matches since joining Fulham on loan in January.

Sky Sports Statto shared his numbers from the second leg of the Championship play-off semi-final, as he inspired Fulham to overturn a 1-0 deficit from the first leg against Derby County:

Brazil are bidding to win their first World Cup since 2002, and they can rightfully expect to contest the latter stages of the tournament at least this year.

They should be beating the likes of Serbia to get there, but the Eagles have the tools needed to cause them problems.