Ryne Sandberg adjusted the top of his lineup Monday, albeit not by choice. Jimmy Rollins tweaked his right groin when making one of three fifth-inning assists Sunday. The 35-year-old shortstop thought it best to rest one day.

His manager agreed. "It'd be smart to get him off his feet today," Sandberg said.

Rollins' absence illuminated one of the formulas behind the Phillies' solid start. Their starting pitching, of course, carried play for more than a week. But the top of the batting order produced with consistency and provided the rest of the lineup with chances.

The Phillies entered Monday with a higher on-base percentage from their top three hitters than any other National League team. Their aggregate .373 clip bested Colorado's .371, although the Rockies led the league in runs at 5.64 per game. The Phillies ranked seventh at 4.07.

A strong on-base percentage is integral for the lineup's top hitters, seeing as they receive more plate appearances than anyone else. And the more runners there are on base, greater are the chances for scoring. Rollins, who has a .347 on-base percentage, has been a major contributor. The shortstop, through one month, improved on his mediocre .317 rate from the last two seasons.

A 1-0 win Sunday over Washington was built on Rollins' swing and speed. He rocketed a Gio Gonzalez pitch to the left-center gap and turned it into a triple. Chase Utley slapped a single up the middle to score Rollins, who carried the day's lone run.

Rollins popped out Monday as a pinch-hitter in the ninth.

Sandberg has employed six combinations for the top of his lineup so far. Ben Revere, Rollins and Utley occupied those spots in 17 of the first 30 games. Tony Gwynn Jr. (.372 on-base percentage) led off six times.

"We've got some versatile guys at the top of the order," Sandberg said. "I have some choices there, yeah. With Gwynn and Revere and Jimmy and Chase, they've been doing a good job of getting on base. That gives us chances to score early . . . That could set the tone for the game."

His other option is catcher Carlos Ruiz, who entered Monday with a .400 on-base percentage. Ruiz batted second for Sandberg three times in the first 30 games. The manager opted for Freddy Galvis, who replaced Rollins at shortstop, in the No. 2 spot Monday.

Extra bases

Cole Hamels felt better Monday, Sandberg said, and his flu symptoms will not prevent him from starting Tuesday. Hamels was bumped from a scheduled Sunday outing. . . . The Phillies have five shutout wins in 2014, which already dwarfs the total of three from 2013. That was their fewest in a single season since 1942.