Mohammad Rizwan underlined why he will be a key weapon for Pakistan at the Twenty20 World Cup, top-scoring in a 21-run win over Bangladesh in Christchurch on Friday. Rizwan maintained his rich vein of form with an unbeaten 78 as Pakistan posted 167-5, before restricting their opponents to 146-8. It was the opening match of a week-long tournament, which also includes hosts New Zealand. All three teams are using it to prepare for the T20 World Cup in Australia. The world’s top-ranked T20 batsman, Rizwan batted through the innings in cold conditions at Hagley Oval, tallying seven fours and two sixes in a chanceless 50-ball knock. It was the 30-year-old’s 21st half-century in the format, continuing his form from last month’s T20 series against England, when he compiled a series-leading 316 runs. His average in the format of 54.34 stands alone among the top 150 run-scorers. The next best is India’s Virat Kohli (50.84). Rizwan’s best support on a tricky, two-paced wicket came from Shan Masood (31 off 22 balls), following an opening stand of 52 with captain Babar Azam (22 off 25) while Taskin Ahmed (2-25) was Bangladesh’s best bowler. Rizwan said being patient after being sent in laid the foundation for a winning score. “Early on the ball was a little bit grippy but me and the skipper decided to keep things simple,” he said. “We did very well but I thought we were 10 to 15 runs short on this kind of pitch. “After that, the bowlers bowled very well to the plan.” Bangladesh’s chase tailed off after Liton Das (35) and Afif Hossain (25) put on a slick 50 for the third wicket from 34 balls. Some late hitting from Yasir Ali (42 not out) restored respectability while speedster Mohammad Wasim (3-24) enjoyed late success with the yorker. Players from both teams regularly slipped on a surface made hard by unexpected weather conditions earlier in the week. A cold blast left ground staff sweeping snow from the covers and outfield on Thursday morning. Temperatures hovered around a relatively warm 12 degrees Celsius (54F) throughout the match, the earliest ever staged in a New Zealand home season. New Zealand will play Pakistan on Saturday and Bangladesh on Sunday, both at the same venue.