Although the decision to replace Pierre Gasly with Alex Albon seems harsh from the outside, it is supported by one simple fact: Red Bull is 44 points behind Ferrari in the constructors' championship this year and Gasly's lacklustre performances have cost the team more than that over the first 12 races. But there are other considerations that would have influenced Red Bull's decision that extend beyond the 2019 season.
The minimum expectation when a driver joins one of the top three teams in Formula One -- be it Red Bull, Ferrari or Mercedes -- is that they finish grands prix in the top six more often than not.