Tennis ranking freezes
When the tours froze the rankings: a chronological account from the 2020 pandemic to long-injury protected entries.
March 2020, Covid suspension
On 12 March 2020 the ATP and WTA suspended all tour events. The rankings were frozen as of 16 March 2020 and stayed frozen until August. When play resumed, both tours adopted a "best-of" counting system to allow players to drop bad results from before the freeze without penalty.
Protected ranking after long injury
A player out for 6+ months can apply for a Protected Ranking, the ranking they held when they were last fit. They can use it to enter a limited number of main-draw events when they return. Andy Murray, Juan Martin del Potro, Caroline Wozniacki and Bianca Andreescu have all used PRs.
Special rankings, maternity
Both tours allow a Special Ranking on return from pregnancy or maternity leave. Serena Williams and, more recently, Naomi Osaka used Special Rankings to access seeded entry on return.
Suspended players
Russian and Belarusian players were not banned from the tour after the 2022 invasion of Ukraine, but they were temporarily ineligible for Wimbledon. The ATP and WTA both controversially refused to award ranking points for that 2022 Wimbledon, leading to ranking distortions for months afterwards.