Oghenekaro Etebo's own goal and a Luka Modric penalty gave Croatia a winning World Cup start against Nigeria in a poor Group D match in Kaliningrad.
Etebo, who joined Stoke City from Portuguese club Feirense for £6.35m on Monday, turned Modric's first-half corner into his own net after Ante Rebic and Mario Mandzukic had both got touches.
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Modric then converted a 71st-minute penalty - Croatia's first shot on target - after William Troost-Ekong had manhandled Mandzukic at a corner.
Nigeria offered little attacking threat, although Dejan Lovren blocked Alex Iwobi's shot just before half-time, and Odion Ighalo glanced a Brian Idowu cross straight at goalkeeper Danijel Subasic.
Victory takes Croatia top of their group, after Iceland held Argentina 1-1earlier on Saturday.
