Šimić made his name with
Dinamo Zagreb where he started his professional football career in
1992. He played for Dinamo for seven seasons, during which the club won five
Croatian First League titles and also became a member of the
Croatian national football team.
Šimić appeared in only one out of four matches played by Croatia at the
Euro 1996, but was then a regular member of the starting line-up at the
1998 FIFA World Cup, where Croatia surprisingly finished third, and appeared in six out of seven matches at the tournament, only missing the third-place match as he was not eligible to play after being given two yellow cards in the previous two matches. His performances in France earned the attentions of Europe's biggest clubs and he went on to join
Inter Milan in January
1999 after also playing with Dinamo Zagreb in the
UEFA Champions League in the autumn of 1998. However, he never established himself as a first-team regular during four years in Inter, and the cross-city rivals agreed a player swap with
Ümit Davala going in the opposite direction in
2002.
He played for Croatia in two out of three group matches at the
2002 FIFA World Cup as well as in all three group matches at the
Euro 2004. The Croatian team was eliminated in the first round on both of these two tournaments. On the club level, he made a more significant contribution with AC Milan including 13 appearances on the road to victory in the 2003
UEFA Champions League, though he was omitted from the
Old Trafford final.
In May 2006, he signed a contract extension with Milan that will keep him at the club until 2009, just weeks after openly criticizing coach
Carlo Ancelotti over lack of playing time.
At the
2006 FIFA World Cup, he appeared in all of the Croatian team's three group matches before they were eliminated from the tournament with two draws and one defeat. The second group match against
Japan on June 18, 2006 in
Nuremberg was also notable for being his 82nd for Croatia, which enabled him to surpass
Robert Jarni's record-holding 81 caps and became the Croatian team's all-time cap leader. In the last group match against
Australia, he was sent off in 85th minute for receiving his second yellow card in the match.
Alongside experienced
Robert Kovač and
Igor Tudor he is considered one of the best Croatian defenders in recent history. Šimić also scored three goals for Croatia and last time he was on target with a last-minute goal for their 3-2 victory in a friendly match against
Argentina on March 1, 2006 in
Basel.
There is a strong speculation that Simic is going to move to
Lokomotiv Moscow during the January
transfer window 2008.