Croatia's Nikola Kalinic was called up on Monday to the Euro 2012 squad to replace veteran striker Ivica Olic as scans showed Olic's right thigh injury was more serious than first feared.
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Ultrasound and MR scans performed on 32-year-old Olic in Munich earlier Monday showed a partial rupture of a right thigh muscle, the Croatian squad doctor said.
"The injury that did not seem serious ... unfortunately proved to be a serious one," squad doctor Zoran Bahtijarevic said in a statement issued by the national football federation.
"Such an injury requires a recovery of between four and six weeks so (Olic) was dropped from the list at the last moment," he added.
Croatia coach Slaven Bilic called up 24-year-old Kalinic, who plays for Ukrainian side Dnepropetrovsk, as a replacement, the federation said.
Olic, who will play for Bundesliga side VfL Wolfsburg next season after signing from Bayern Munich, suffered the injury during Saturday's 1-1 draw with Norway in Oslo.
It is the latest in a long line of injuries that Olic has been plagued by in the past two years as he has also been dogged by knee problems and a hip injury.
Croatia - for whom Olic was a key member in Euro 2008 when they reached the quarter-finals - face a tough task in progressing from their group as they have been drawn in Group C with champions Spain, Italy, and the Republic of Ireland.
The former Yugoslav republic play their first match at the championship, hosted jointly by Poland and Ukraine, against Ireland on June 10 in Poznan, Poland.