Atlético de Kolkata travel to Mumbai City FC for the second leg showdown of the first semi-final of Hero Indian Super League 2016 at the Mumbai Football Arena on Tuesday evening. The 2014 champions, who now have gone seven games without a loss, scored thrice against the best defence in the league in the first leg but also conceded twice for a slender one-goal advantage. However, their away form has been better this season, with three out of their five overall victories coming on the road. Be that as it may, Jose Molina’s men will have to tighten their defence going into this crucial tie. Their opponents Mumbai City FC showed good attacking prowess in the first leg and ensured ATK did not take any significant advantage from the match. Still, what may hurt them could be the absence of marquee man Diego Forlan, who is serving a one-match suspension on account of a red card in Kolkata. It will be interesting to see how Mumbai cope with the absence of the legendary Uruguayan.Head-to-Head: The inaugural season of the Hero ISL saw ATK brush aside Mumbai 3-0 at Kolkata before the eventual champions were edged 2-1 in Mumbai. Hero ISL 2015 witnessed Kolkata rout Mumbai 4-1 away before they were pipped 3-2 at home. This season saw the two teams play out a 1-1 draw in Mumbai before ATK were beaten by a sole Diego Forlan winner at home. In the first leg of the semi-final between the two sides in Kolkata, ATK edged Mumbai 3-2.Form Guide (last five matches):Mumbai City FC: D-W-W-D-LAtlético de Kolkata: D-W-D-D-WGerson Vieira vs Helder PostigaGerson Vieira was undoubtedly Mumbai’s star from the last match. The 24-year-old Brazilian defender earned the free-kick before heading home for Mumbai’s second goal of the night. However, in this must-win tie, which Mumbai need to win by at least a two-goal margin, Vieira has to ensure they don’t concede too many.Kolkata’s marquee player Helder Postiga has shown great attacking flair so far. With decisive touches and crisp passing, the Portuguese has led many an attack and created a host of chances for his team. He was at his clinical best in the first leg, making crucial attacks besides winning the penalty which was converted by Iain Hume. ATK would need him to have another good outing.Leo Costa vs Sameehg DoutieOne of Mumbai’s most influential midfielders this season, Brazilian Leo Costa was at his deadly best in the first leg. He scored his team’s opening goal and showcased some good football all through the match. Possessing quick feet and the ability to finish clinically, the 30-year-old will again need to be top-notch while pulling the strings from the middle of the park going into Tuesday’s match.ATK’s Sameehg Doutie has displayed some good, skilful football after returning from injury. With two goals and three assists overall, the South African winger has again been an influential factor in Kolkata’s campaign. He provided the assist for Hume’s first goal in the first leg, and kept the opposition defence on its toes all through the match. He will again hold the key on Tuesday.Sunil Chhetri vs Prabir DasMumbai’s Sunil Chhetri has not exactly got going as far as his ISL campaign so far is concerned. However, he has time and again proved his importance in big games. His capabilities are well known and he can change the complexion of the game in the blink of an eye. With his team in a must-win situation, and with the in-form Forlan missing, it can be expected that the India captain will come all guns blazing.ATK’s Prabir Das has been one of the exciting young talents this season. The 22-year-old right-back possesses good speed and sound defensive technique, making him not only a tough player to outwit as an attacker but also a very useful attacking option from the right flank. He can whip in good crosses and makes important tackles, interceptions and clearances. With Mumbai needed to be on attacking mode tomorrow, the youngster is likely shoulder a lot of responsibilities in keeping the opposition at bay.Squads:Mumbai City FC: Roberto Volpato Neto, Amrinder Singh, Albino Gomes, Gerson Vieira, Lucian Goian, Facundo Cardozo, Anwar Ali, Aiborlang Khongjee, Lalhmangaihsanga Ralte, Lalchhuanmawia Fanai, Ashutosh Mehta, Krisztian Vadocz, Leo Costa, Jackichand Singh, Saran Singh, Sehnaj Singh, Boithang Haokip, David Lalrinmuana, Matias Defederico, Otacilio Brito Alves, Sony Norde, Thiago Cunha, Sunil Chhetri, Udanta SinghAtlético de Kolkata: Debjit Majumder, Dani Mallo, Shilton Paul, Arnab Mondal, Henrique Fonseca Sereno, Jose Arroyo, Keegan Pereira, Kinshuk Debnath, Prabir Das, Pritam Kotal, Robert Lalthamuana, Abinash Ruidas, Bidyananda Singh, Bikash Jairu, Bikramjit Singh, Borja Fernandez, Javi Lara, Jewel Raja, Lalrindika Ralte, Ofentse Nato, Sameehg Doutie, Stephen Pearson, Helder Postiga, Iain Hume, Juan Belencoso /