Foster played 7 Tests, 11 ODIs and 5 T20Is for England.
Foster replaced former Assam cricketer Subhadeep Ghosh in his role. The 39-year-old played 7 Tests, 11 ODIs and five T20Is for England from 2001 to 2009 and bid farewell to professional cricket two years back before pursuing his coaching career.
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Foster will be joining a revamped KKR coaching staff, including the team's former opener and skipper Brendon McCullum in head coach's capacity and ex-New Zealand pacer Kyle Mills as the team's bowling coach. David Hussey, the former Aussie batsman, had been roped in as KKR's chief mentor.
Despite two-time champions enduring lacklustre campaigns in the last couple of seasons, the team management decided to continue with skipper Dinesh Kartik for the IPL 2020 that begins on March 29.