{| class="wikitable" style="margin-left:1em; text-align:center;"
! style="width:60px;"|Rang.<ref name="atp">[[ATP's verdensrangliste]] pr. [[1. februar]] [[2021]].</ref>
! Spiller
! Årsag
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| 5
| style="text-align:left; padding-left:5px; padding-right:20px;"|{{flagikon|SUI|3:2}} [[Roger Federer]]
| style="text-align:left; padding-left:5px; padding-right:20px;"|[[Knæ]]skade<ref>[https://ausopen.com/articles/news/australian-open-media-statement-roger-federer-withdraws Australian Open - ''Australian Open Media Statement: Roger Federer withdraws'' (28. december 2020)] {{en sprog}}</ref> eller familiære årsager<ref>[https://www.eurosport.com/tennis/australian-open-5/2021/roger-federer-s-ausralian-open-withdrawal-due-to-family-not-injury-tennis-australia-official_sto8056351/story.shtml Eurosport - ''Roger Federer's Australian Open withdrawal due to family not injury - Tennis Australia official'' (7. januar 2021)] {{en sprog}}</ref>
|-
| 22
| style="text-align:left; padding-left:5px; padding-right:20px;"|{{flagikon|CHI|3:2}} [[Cristian Garín]]
| style="text-align:left; padding-left:5px; padding-right:20px;"|[[Håndled]]sskade<ref>[http://www.tennisnow.com/Blogs/NET-POSTS/January-2021-(1)/World-No-22-Cristian-Garin-is-out-of-the-Australia.aspx Tennis Now - ''World No.22 Cristian Garin is out of the Australian Open with Wrist Injury'' (12. januar 2021)] {{en sprog}}</ref>
|-
| 24
| style="text-align:left; padding-left:5px; padding-right:20px;"|{{flagikon|USA|3:2}} [[John Isner]]
| style="text-align:left; padding-left:5px; padding-right:20px;"|Familiære årsager<ref>[https://www.atptour.com/en/news/isner-not-playing-australian-open-2021 ATP Tour - ''Isner Will Not Play Australian Open: 'It Wasn't An Easy Decision'' (12. januar 2021)] {{en sprog}}</ref>
|}
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