Slovenia head coach Srecko Katanec believes in-form England striker Harry Kane still has to improve to be considered among the world's top players.
Katanec's men play at Wembley on Thursday evening knowing that anything other than victory will leave them relying on other results in their quest to qualify for next summer's World Cup.
Keeping Kane quiet will be key to that with the Tottenham man having struck 13 goals in 11 appearances for club and country this season.
Although Katanec appreciates the talents of the 24-year-old, he does not think he can yet be regarded alongside the likes of Lionel Messi and Cristiano Ronaldo.
"We will need to defend on him really strictly, maybe sometimes put two defenders on him,'' Katanec said about Kane, who will captain England for the game.
"I know he's a great player, but I cannot say he's at Ronaldo's level.
"He's definitely coming to that but the thing that worries me is that he scores too many goals in the last period.''
While Group F leaders England need two points from their two remaining games to guarantee qualification, Slovenia's only realistic route to Russia is via the playoffs.
They are currently six points adrift of Gareth Southgate's side and are battling Scotland and Slovakia for second and a potential two-legged play-off in November.
Their hosts have not lost a competitive game at Wembley for almost 10 years, and 54-year-old Katanec is aware of the tricky task facing his team.
"We need to be very solid in defence, we need to help each other, we need to be compact on the pitch,'' he added.
"That's the only way to achieve success.''
Slovenia, who trained on the Wembley pitch on Thursday afternoon and have a fully-fit squad for the fixture, have never beaten England, losing four of five previous meetings.
They did, however, record a point against the Three Lions earlier in the qualifying game following a dull goalless draw in Ljubljana last October.
Captain Bostjan Cesar thinks his side can take confidence from that result in order to keep alive their qualification hopes.
"We were close to winning that match and we are positive about tomorrow,'' said the experienced Chievo defender, who had a loan spell at West Brom during the 2007-08 season.
"We will try to achieve a positive result because this is the only result which will keep us in the game.''