India were on the threshold of becoming the number one team in Cricket Test rankings as they closed in on an emphatic victory in the third and final Test against Sri Lanka despite captain Kumar Sangakkara's gritty unbeaten century at Mumbai on Saturday. Sangakkara 133 and Nuwan Kulasekara 9 were at the crease. The Lankans are still trailing by 59 runs at the end of the day.After conceding a mammoth 333-run first innings lead, the visitors were struggling at 274 for six at close on the penultimate day.The Indians, on the other hand, will look to wrap up the remaining four wickets quickly on Sunday and clinch the three-match Test series with a 2-0 margin.The Sri Lankan captain Sangakkara notched up his 21st Test century, his maiden one in India.Sri Lanka's hopes of staving off defeat entirely rest on Sangakkara who has to bat out the entire day along with the tailenders or take a big enough lead which will take the game out of India's grasp.Resuming at the overnight score of 11 for no loss, the Lankans needed a solid start from their openers but that did not happen.For India P.Ojha and Zaheer Khan took two wickets each and Harbhajan Singh and Sreesanth one each.