FC Goa became the third team after defending champions Atlético de Kolkata and Delhi Dynamos FC to reach the 2015 Hero Indian Super League semi-finals following their 5-1 win against Kerala Blasters FC at the Jawaharlal Nehru Stadium in Kochi on Sunday. There is now just one spot up for grabs and four teams are in the fray for that spot. These are NorthEast United FC, FC Pune City, Chennaiyin FC and Mumbai City FC. Last-year finalists Kerala Blasters FC are the only team right now to have been out of contention. Here is how the Highlanders, the Stallions, the Super Machans and Mumbai City FC can clinch the fourth semi-final spot heading into the last week of the league stage.NorthEast United FC: The Highlanders have 17 points from 13 matches with a goal difference of -6 and in their last match of the league stage they play FC Pune City on December 2. They will have to beat the Stallions first and then hope that Chennaiyin FC lose one of their two remaining matches. If these two results come the Highlanders’ way, they will be through to the semis.Chennaiyin FC: The Super Machans have 16 points from 12 matches and a goal difference of 6. If they win both their matches (vs Mumbai City FC on December 1 and vs FC Pune City on December 5), they will be through to the semis. However, even four points from these two matches might be enough for them to advance ahead of NorthEast United FC as they enjoy a much better goal difference than the Highlanders.FC Pune City: The Stallions, who have 15 points from 12 matches with a goal difference of -4, will have to beat NorthEast United FC and Chennaiyin FC to secure themselves a place in the semis.Mumbai City FC: Among the four teams, Mumbai City FC (13 points from 12 matches) are the only team with very remote hopes. Not only will they have to beat Chennaiyin FC and Atlético de Kolkata (on December 4), they will also have to hope that NorthEast United FC lose against FC Pune City and Chennaiyin FC draw against FC Pune City. If these results come Mumbai’s way, they will be level on 19 points with FC Pune City but they may still not be able to qualify as they have a goal difference of -8 as compared to -4 of the Stallions as of now, and that means they will have to register really big wins against Chennaiyin FC and Atlético de Kolkata. If FC Pune City and Mumbai City FC’s goal-differences end up being the same, then the team scoring the most number of goals in the league stage will advance. If again, there is a stalemate as regards the number of goals, then the Stallions will go through on the basis of having taken four points from the two league games against Nicolas Anelka’s men earlier in the season.