"He was starting to get his swing down," Manuel said.
The second baseman already missed the first 46 games of the season with patellar tendinitis in his right knee. In his recent week sidelined, Utley was cleared twice by Impact tests designed to ascertain the severity of the concussion. But for the second straight season, he'll accrue fewer than 600 plate appearances after five straight years of eclipsing that mark.
And since the beginning of August, Utley's numbers are in a sharp decline. After a 2-for-4 night Aug. 1, Utley was hitting .290 with an .878 OPS. He's hitting .214 with a .619 OPS in 30 games (137 plate appearances) since then.
Most concerning is Utley's inability to drive the ball on a consistent basis. His line drive rate of 12.3 percent is the lowest in baseball for players with at least 300 plate appearances. Utley's career line drive rate is 20.3 percent.
Manuel said he saw promise after an 0-for-7 showing Sept. 4 in Florida. Utley had three hits - two for extra bases - and scored four runs in two games against Atlanta on Sept. 5 and 6.
"He was starting to drive some balls and get his swing down," Manuel said. "Then he got hit in the head, and it set him back. But he has time to get ready. When we do get into the playoffs, he'll be ready."
The Phillies will play a majority of American League East foes during interleague play in 2012 and open in the state of Pennsylvania but not at home.
Opening day is in Pittsburgh's PNC Park on April 5. Phillies fans overran Nationals Park in Washington for opening day in 2010, and this could be an encore.
The highlight of the interleague schedule is a trip to Baltimore for the team's first games at Camden Yards since 2006. At the advent of interleague play, the Phillies and Orioles were "natural" rivals and played every season from 1999 to 2006.
The Phillies will also travel to Minnesota for the first time since 2004. It will be their first games in Target Field, which opened in 2010. The other American League road series is in Toronto for the second straight season.
Yet again, the Boston Red Sox will spend a weekend at Citizens Bank Park, from May 18 to 20. The other home interleague series is against the Tampa Bay Rays.
Just like this season, the Phillies will spend the majority of September and October on the road. Eighteen of their final 30 games are away from home. The season ends with a six-game road trip to Miami and Washington.
The home opener is April 9, a Monday, against the Marlins. The Phillies make an early West Coast trip with 10 games in San Francisco, San Diego, and Arizona from April 16 to 25.
The Phillies will start Kyle Kendrick in Game 1 of the doubleheader against Florida on Thursday. He'll oppose Anibal Sanchez. In the nightcap, Cliff Lee faces righthander Alex Sanabia, who has thrown only one inning in the majors this season. . . . The Phillies do not plan on adding any extra pitchers or position players from the minors for the doubleheader.
Contact staff writer Matt Gelb at email@example.com or @magelb on Twitter.