New Delhi, May 20 : Former India cricketer Harbhajan Singh opined young Rinku Singh was the X-factor for Kolkata Knight Riders (KKR) this season and not star all-rounder Andre Russell. Rinku has been the standout performer for the two-time IPL champions. He has scored 407 runs in 13 matches this season at a strike rate of 143.31 and an average of 50.88. "Now Rinku has become the X-factor for KKR, not Russell. Russell's era is gone. It's Rinku's time now. Even if Rinku is sent up, he can do justice to his role. He is a player of different calibre and we will soon see an India cap on his head," Harbhajan said while speaking on Star Sports' Cricket Live. Meanwhile, former India chief coach Ravi Shastri said that Rinku is the star of the KKR team and has a very strong attitude. "Rinku Singh is the hero of Kolkata Knight Riders. His temperament is very strong and gets very comfortable in tough situations. He's a battle-hardened player. Rinku likes close matches and this ability to do well in crunch situations is what separates this player from others," said Shastri. /IANS