SAN DIEGO — While their best player visited the doctor and their offense remained absent, the Washington Nationals’ starting rotation again made anything seem possible. Ryan Zimmerman can flirt with the disabled list, and their starting eight position players can scrape together two hits. Send Gio Gonzalez to the mound, and nothing else matters.

Tuesday night, while Zimmerman received an MRI that returned unfavorable results, Gonzalez delivered another dazzling start in a 3-1 victory over the San Diego Padres before 16,599 at Petco Park. Gonzalez fired six shutout innings, running his personal scoreless streak to 20 innings and lowering his ERA to 1.52. Gonzalez allowed two hits, increasing his total over his 20 innings of zeros to a scant six.

Gonzalez out-dueled left-hander Clayton Richard, who held the Nationals hitless for four innings and scoreless for six. They finally broke through in the seventh, when Chad Tracy reprised his season-opening role as an off-the-bench hero with a two-run, pinch-hit single.

“We got to scratch and claw to try to get a get a couple runs,” Manager Davey Johnson said. “We’ve got to be perfect with our pitching.”

So far, their pitching has tested the limits of how feeble a staff can make major league hitters. They own a 2.21 ERA, including a 1.72 ERA among their starting five. Moments after Henry Rodriguez pumped 100-mile-per-hour fastballs and mind-bending, high-80s changeups in the ninth to polish off his fifth save, the Atlanta Braves beat the Los Angeles Dodgers, 4-3 — a result that gave the Nationals, at 13-4, the best record in the National League.

“It’s exciting, because we as players were talking about it, we’re not really firing on all cylinders right now,” reliever Tyler Clippard said. “But we’re 13-4. We’ve got a lot of the pieces in place, and we’re going to start swinging it eventually. If we go through our lulls, we can pitch our way through them. That’s the exciting thing about this club.”

The Nationals possess an impotent offense and a crowded trainer’s room, but their rotation covers up those and any other ills. After Gonzalez’s latest tour de force, Nationals starters have thrown 22 consecutive scoreless innings, which is only their second longest such streak this season; they had a 23-inning scoreless streak, too. In 13 of 17 games, the Nationals’ starters have allowed two or fewer earned runs.

And yet, their offense makes them sweat it out, night after night. Richard matched Gonzalez zero for zero until the sixth, when the Nationals finally broke through. Xavier Nady scalded a double to left field, only the second hit off Richard all night. Wilson Ramos drew a walk, and Steve Lombardozzi bunted both runners into scoring position.

With his spot in order due up, Gonzalez’s night had ended after 91 pitches. “He had a lot more left in him,” Johnson said, but one byproduct of a crummy offense is pulling the starter sooner than you’d like. The Nationals obviously needed a pinch hitter, but who?

With Zimmerman out and Richard starting, his usual right-handed pinch-hitting candidates — Nady, Mark DeRosa and Lombardozzi — were already in the game. Johnson, not wanting to burn backup catcher Jesus Flores so early, had no choice but to send up a lefty.