I would put Devvarman and Johnson together along with Pernfors.
Devvarman beat Isner twice within a few days down in Athens in the 2007 NCAAs. He first beat him in straight sets in the NCAA team Semifinals. Remember, that 2007 Georgia team was considered one of the greatest of all time. Then, he beat him again in their classic 3 set Singles Final.
Pretty impressive to beat your top rival in a hostile environment on his home courts. Especially when you do it twice within a week.
Also keep in mind that Devvarman beat Kevin Anderson in the semifinals in the Athens NCAAs (after beating him earlier in the season).
Anderson is currently a top 30 pro.
Johnson really didn't have a rival to speak of who could push him.
Devvarman's only loss that year was in the Tulsa wind. I don't believe Johnson ever won the All-American event.
While Devvarman's teams didn't accomplish what Johnson's did, it wasn't because of Devvarman. I believe he won every singles match in the NCAAs at least his junior and senior years.
3 straight NCAA singles Finals is a tough stat to accomplish
Originally Posted by Don't Let It Bounce
Somdev Devvarman was in three straight NCAA finals, winning the second and third. One of those years he beat Isner in the finals. (I realize, of course, that doesn't eliminate Isner from consideration.) He went 44-1 one year, too.
I'm not knowledgeable enough of college tennis to say those achievements are the bottom line, but they are the most impressive I know of.