Kevin O'Brien has made the second-best start in terms of ICC rankings points for a batsman playing for a debutant Test team.
O'Brien made 40 in Ireland's first innings against Pakistan in Malahide, and 118 in their second innings, to set up the possibility of a fairytale victory after being made to follow on. That performance earned O'Brien 440 rankings points.
To find a performance that earned a batsman more rankings points in a team's debut Test, we must go all the way back to 1877 and the first ever Test match, in which the opener Charles Bannerman made 165 retired hurt out of Australia's first-innings total of 245 against England at the MCG. One hundred and forty one years later, that innings still holds the record for the highest share of a team's total made by one batsman. That performance earned Bannerman 447 ICC rankings points, retrospectively.
O'Brien snuck in between Bannerman and Aminul Islam, whose innings of 145 in Bangladesh's inaugural Test against India in 2000 earned him 432 points. Dave Houghton's 121 and 41 not out in Zimbabwe's maiden Test against India in 1992, meanwhile, fetched him 431 points.