Former Indian wicketkeeper Dinesh Karthik expressed surprise at Rohit Sharma becoming No. 1 in the ICC ODI batter rankings for only the first time in his career. Thanks to his incredible showing in the recent three-match ODI series in Australia, the veteran opener rose to the mountaintop in the latest standings.Yet, Karthik questioned how Rohit had never been ranked No. 1 in ODIs despite his stellar numbers, especially during the 2019 World Cup. For the uninitiated, Rohit Sharma enjoyed an incredible run in the tournament, finishing as the leading run-scorer with 648 runs at an average of 81, including a record five centuries.Talking about Rohit's ascent to the top of the ODI rankings after the first India-Australia T20I, Karthik said on Cricbuzz (24:39):"I am surprised that in the 2019 World Cup he wasn't No. 1 somewhere during the tournament. Just the way he batted, it was poetry in motion. It was fascinating to watch how much effort he put in in the lead up to the series. Prior to this series, the last three to four years, when the ball was seaming, his only modus operandi was hit out or get out. Here he actually went back to being a good old fashioned opener, where he left the ball and played defense. He almost showed what it took to do well in such tough conditions as an opener."He continued:"Now that side of Rohit Sharma we haven't seen because the beligerent side we've become so accustomed to. That's an even harder skill but this is a hard skill in a different way. It takes a lot of mental courage to leave a ball, get no success out of it because it's a dot ball. Yet know that if I bat through this and back my technique, I'll get runs."Rohit also became the oldest to be ranked No. 1 on the ICC ODI batter rankings at 38 years and 182 days.How Rohit Sharma reached the top spot on the ICC ODI rankingsRohit Sharma replaced his successor as captain, Shubman Gill, at the top spot on the latest ICC ODI batter rankings after the Australian ODI series. The former scored a sparkling unbeaten century in India's final ODI win over Australia in Sydney.Rohit also scored a well-paced 73 on a challenging pitch in Adelaide in the second ODI. It meant the star batter finished as the series' leading run-scorer with 202 runs at an average of 101.Meanwhile, Gill endured a rare poor run in ODIs in the Australian series, scoring only 43 runs in 13 innings. As a result, the Indian captain slipped to No. 3 on the rankings, with Rohit moving to the top.