FORT MYERS, Fla. -- Red Sox slugger David Ortiz took another down day from running on Friday, making it obvious that he won't reach the original target of playing in an exhibition game by the end of this week.

Coming off a right Achilles injury, every activity Ortiz participates in needs to be based on symptoms, and Boston's designated hitter still has enough soreness that he typically can't run the bases two days in a row.

"He'll take batting practice and go through the drill work but no running today," said manager John Farrell. "Hopefully [he will run] again tomorrow. As he has mentioned himself, there are days we have to adjust at the moment. I know David is frustrated by it and we'll continue to go day to day with it."

At this point, the Red Sox aren't ready to rule Ortiz out for Opening Day, which is April 1 at Yankee Stadium.

"We haven't gotten to that point yet, no," Farrell said. "We feel like even now, with Minor League games starting up, we'll still be able to get the appropriate number of at-bats that he'll feel comfortable with -- provided there's progress being made. That's the status of day to day."

There are few players in Boston's lineup as critical to the team's success as Ortiz. Perhaps that's why Farrell hasn't contemplated a "Plan B" just yet in the event Ortiz isn't ready to go when the Sox break camp.

"He's critically important to our lineup," said Farrell. "He's aware of that. I think that's what adds to his frustration of not being able to get on the field and participate in Spring Training and get ready for the regular season, because we haven't come to that date yet where 'OK, plan B is now a legitimate one.' I know those discussions will take place, but we're still hopeful that he will be ready. But we've got to be aware that that may need adjusting."

Ortiz has stated he'd like to get about 50 at-bats before the season starts. At this point, Farrell said that Ortiz isn't seeking a second opinion for his Achilles, which was originally injured nearly eight months ago.

Boston's training staff remains confident that Ortiz is still having routine soreness from the original injury, and that a subsequent ailment hasn't developed.

"Every indication is that right now -- yes," Farrell said. "That this is part of getting back in shape and it's volume and intensity related. There isn't the thought of any kind of re-injury or injuring anymore then what was sustained last year."

Drew out of lineup due to mild concussion

FORT MYERS, Fla. -- Red Sox shortstop Stephen Drew didn't play Friday night due to what the club believes is a mild concussion, sustained when he was hit by a pitch on Thursday against the Twins.

"Throughout the night, there were some symptoms of a mild concussion that came on after being hit by the pitch yesterday," said manager John Farrell. "That's why he was in the lineup initially and then when he came in, [we] determined that we've got to give it a day or two to clear up."

At first, Drew seemed unfazed by the pitch that hit his batting helmet.

"At the time, he was like, 'Imagine if this hit me in the nose.' Fortunately it glanced off the helmet, and in the way he reacted, you'd almost think he didn't see the pitch completely," Farrell said. "There wasn't a whole lot of diving out of the way. It wasn't a direct blow. At the time, he felt fine throughout the game. But it was last night when he started to read a book, the print started to get a little fuzzy on him and that's where -- obviously it was precautionary, and, by rule, he's being held out."

Teams are required to follow specific MLB guidelines while dealing with concussions.

"Dr. [Gary] Green in New York, who is responsive, whether it's weekends or not, that's the doctor we'll go through," Farrell said. "It's checking those symptoms in the training room, and then if need be, there's an on-line test he'll have to go through if we get to that point."

Nava making smooth transition to first base

FORT MYERS, Fla. -- Daniel Nava continues to get work at first base and was in the starting lineup at that position for Friday night's game against the Twins.

Entering Friday, Nava had played eight innings at first this spring.

Manager John Farrell has already seen enough good things from Nava at the position to be comfortable putting him there during a regular-season game.

"He's made the transition in incorporating the position pretty seamlessly. His hands, his feet work fluidly," said Farrell. "The timing of it is good. He's been able to shorten up his arm stroke on the front end of a double play. It's been very encouraging."

Nava's versatility to play the outfield and first base, to go along with his on-base skills, could give him an inside track in the competition for one of Boston's bench spots.