In his brief statement to the Judiciary Committee (beginning at 16:55 of the link for Roberts' statement at this C-Span page), John Roberts twice likened a judge's role to that of an umpire:

At 18:53: Judges are like umpires. Umpires don't make the rules, they apply them. The role of an umpire and a judge is critical to make sure everybody plays by the rules. But it is a limited role. Nobody ever went to a ballgame to see the umpire. . . .

At 21:55: I'll remember that it's my job to call balls and strikes, not to pitch or bat.

Roberts' comparison of a judge to a baseball umpire reminds me of an old story about three different versions of judicial reasoning, built on the same analogy.

First umpire: "Some are balls and some are strikes, and I call them as they are."

Second umpire: "Some are balls and some are strikes, and I call them as I see 'em."

Third umpire: "Some are balls and some are strikes, but they ain't nothin' 'til I call 'em."

Three views of legal reasoning are represented here, with the first umpire representing some form of essentialist jurisprudence such as so-called "mechanical jurisprudence." The second umpire would be close to the role attributed to a traditional judge in a liberal democratic society, believing in the existence of truth and in the wisdom of attempted impartiality, but also in the imperfection of people to see or understand truth. The view of the third umpire is usually attributed to legal realism or critical legal studies, though it would fit only a subset of adherents to those quite different philosophies.

While I think that Roberts with his talk of modesty was expressing a belief in the second sort of umpire, one should realize that the analogy of the umpire can cover the third sort, who thinks that he creates the existence that he is assigned to judge.

Further, I have heard that in Major League Baseball, umpires are rated on how well they call balls and strikes and demoted (or at least influenced in their future calls) if they call balls and strikes poorly. I question whether the press provides a similarly effective role judging the performance of justices.

UPDATE: Lest you think that no real umpire would express the third position, it turns out that the last view was based on a statement from a Hall of Fame umpire who died in 1951, Bill Klem. About whether a pitch was a ball or strike, Klem said, "It ain't nothin' till I call it." (Tip to readers Stephen Kaus and Craig Oren.)