'Growing concern' Red Sox's Uehara won't be ready for Opening Day

The thought of starting the season without closer Koji Uehara is becoming more of a reality for the Boston Red Sox. 

"With each passing day he's not in a game, there's growing concern of, 'will he be ready for April 6?'" manager John Farrell told Tim Britton of the Providence Journal. "We're just working through that."

Uehara suffered a minor hamstring strain while running last week, though he has been long tossing from flat ground. 

Following the injury, the right-hander said he wouldn't need to go on a rehab assignment before jumping back into the bullpen. However, Farrell appears inclined to let him see some hitters before using him in a game. 

"It's important to see him in games, to evaluate the stuff, and for Koji himself to understand what he has in the moment and what he goes to the mound with from a physical standpoint," Farrell said. 

Uehara, who agreed to a two-year, $18-million extension in October, posted a 2.52 ERA and 26 saves in 64 appearances last season.