Portugal may have 'one of the best players in the history of football ' in the form of Cristiano Ronaldo but Branislav Ivanovic is confident his Serbia side can nullify the threat of the Real Madrid star on Sunday night . Serbia currently occupy fourth place in the Group I standings ahead of their clash with Portugal who sit just one point behind pool leaders Denmark . 'You 're speaking about one of the best players in the history of football , he 's not so easy , ' Ivanovic told Perform . Cristiano Ronaldo ( left ) vies for possession with Jose Fontes during Portugal training on Thursday . Ronaldo , Ricardo Quaresma ( left ) and Vieirinha are gearing up for the visit of Serbia on Sunday night . 'To be on the top level you have to prove yourself every day , he 's doing that game by game . 'He is the guy who knows how to deal with the pressure , for us it will be a big challenge and I hope and I know we have the quality to try to deal with that . ' Ivanovic 's side were deducted three points following their 3-0 win against Albania in October when an unmanned drone carrying a pro-Albania flag flew over the Partizan Stadium in Belgrade and resulted in a melee between the two sets of players and some Serbian fans . A 3-1 loss to Denmark in November has heaped further pressure on Serbia and Ivanovic concedes that Sunday 's game is a must-win game for his side . Branislav Ivanovic ( left ) is hoping a win over Portugal can re-ignite Serbia 's bid to reach Euro 2016 . 'It is a crucial game for us , this qualification especially , because we expect to have more points in the three games , so the game against Portugal is crucial and massive for us , ' the Chelsea defender added . 'We know Portugal is favourite and are a great team but they 've lost a game at home against Albania , so we see our chances and we know if we perform well - if we play to the level we know how to play - we can expect some presents and gifts from the game . ' Serbia were deducted three points following their 3-0 win against Albania in October when an unmanned drone carrying a pro-Albania flag flew over the Partizan Stadium in Belgrade resulting in ugly scenes .
Serbia face Portugal in Group I on Sunday night . Branislav Ivanovic 's side are currently in fourth place with a solitary point . Serbia were deducted three points following their 3-0 win over Albania .