Zigic nodded home the winner from Sebastian Larsson's cross in yesterday's 1-0 win at Upton Park to move Birmingham out of the relegation zone and send rivals West Ham back to the foot of the table.
The 6ft 7in Serbian initially struggled to cope with the demands of English football after his ?6million move from Valencia last summer, but has now scored in successive league games and caused problems for the Hammers defence throughout yesterday's clash.
Saint Nik: Zigic (centre) has now scored in back-to-back league games, much to the delight of boss McLeish
'He's upped his game. He's at a good level now," McLeish said of the 30-year-old.
'He's an international player and it's been a challenge getting used to England.
'He's beginning to hold his own. He was pushed in the back for the goal but he managed to stay firm and get his head on it.
'He's making his mark and has been powerful for us in the last three of four games.
'If he can continue to cause havoc and create assists then he`ll chip in with one or two himself.'
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Explore more:People: Alex McLeish, Sebastian Larsson Places: Birmingham, United Kingdom