I agree he might have been on a par with Sampras but in terms of him being closer to the Big Three than someone behind him was to him, I don't agree.
Rafa versus Andy 7-17
Fed versus Andy 11-14
Nole versus Andy 11-25
Andy versus Stan 11-8
I think Andy and Stan, both three time Slam winners, are by now inextricably linked as a two-man buffer zone between the demigods and mere mortals.
I enjoy watching Stan more than Murray but Murray is easily superior to Stan.
Outside grand slam wins, Murray has Stan beat in pretty much every category, and it's not really close in a lot of them.
GS Finals: 11-4 Murray
GS Semis: 21-8 Murray
GS Match Wins: 189-139 Murray
GS Match Win Percentage: 81%-72%
Overall Titles: 45-16 Murray
Majors Conversion Rate: 6.3%-5.4% Murray
Overall Match Wins: 663-501 Murray
Career Match Win Percentage: 78%-63% Murray
Overall Titles Conversion Rate: 19.2%-5.5% Murray
Masters Titles: 14-1 Murray
Olympic Gold: 2-0 Murray
Tour Finals: 1-0 Murray
Year-End Number One: 1-0 Murray (Wawrinka never finished higher than 4th)
Weeks at Number One: 41-0 Murray (Wawrinka hasn't been ranked higher than 3rd)
H2H vs one another: 11-8 Murray
Wins vs top 10 players: 101-55 Murray
Wins vs players who have been in the top 10: 304-173 Murray
Wins vs big three: 29-12 Murray
Seasons winning 4+ titles: 6-2 Murray
Davis Cup Record: 39/47-26/51 Murray (both have 1 DC title, but Stan had Roger as his teammate while Murray's second best player was a distant joint second between Kyle Edmund and Dan Evans...)
Also, in terms of consistency in year end rankings, Murray wins big time as well as he was a top 4 player yearly from 2008 till his hip injury in 2017, which is almost a decade. Wawrinka was only a top 5 player from 2013-17, while he's been a top 15/20 player at best for much of his other years.
Murray: 1-2-3-4-4-4-4-4-6
Wawrinka: 4-4-4-8-9
With all that said, Murray isn't nearly good enough in comparison to Fedalovic for it to be a big four, even though he's significantly better than everyone else