"His back's barking a little bit," said Gibbons, who noted that Johnson wasn't available off the bench for Thursday's game versus Detroit. "Hopefully, it's nothing. He had it a little in Spring Training, and it just flared up on him."
The injury first became an issue shortly after Johnson reported to Spring Training in mid February. The problem was in Johnson's lower back, and it caused additional discomfort in his right oblique muscle -- mainly when he ran out of the batter's box.
Johnson received a cortisone shot at the time, and he sat out for a little more than two weeks before appearing in his first spring game on March 8. Gibbons said Thursday that Johnson hasn't received another shot, and he wasn't sure what the team's trainers had planned for the outfielder.
"I don't know what they'll do," Gibbons said. "I don't know if it's the exact spot, but he's having similar pain."
Gibbons said Johnson's status was day to day, but Toronto's manager wasn't sure if the left fielder would be available on Friday. Through seven games, Johnson is hitting .265 with one home run and seven RBIs.
Coming attraction: The Blue Jays just became the unexpected host for the next installment of Dice-K mania.
Boston's game against Seattle was rained out on Thursday, pushing Japanese starter Daisuke Matsuzaka's next start back one day. That means Matsuzaka will take the mound at Rogers Centre on Tuesday night when the Blue Jays open a three-game series against the rival Red Sox.
"I saw him in Spring Training a lot, obviously. All his games were on TV," Jays center fielder Vernon Wells said. "I'm sure he's going to be as good as advertised. We'll just have to be better."
Wells has never faced Matsuzaka, but he saw the right-hander pitch in 2004, when the outfielder headed overseas for Major League Baseball's Japan All-Star Series. Wells knows that brief glimpse won't help him much once he steps up to the plate.
"Nothing helps until you get into the box against guys you haven't seen before," Wells said. "It takes a couple of at-bats to get an idea of what all their pitches are and what they're going to do. He's going to be no different."
The last-minute change likely will bring a flood of media requests from numerous Japanese outlets. The Blue Jays have a football press box down the left-field line, which may or may not be rented out for Tuesday's game. If it is, the club may have to turn part of Windows Restaurant in center field into an auxiliary press box.
League update: Brandon League is about to take another step in the wrong direction in his quest to work his way back into Toronto's bullpen. The Blue Jays plan on placing the right-hander on the 15-day disabled list within the next few days.
League, who was optioned to Triple-A Syracuse on March 25, arrived at Spring Training as the favorite to be Toronto's setup man this season. That was until faulty mechanics, which stemmed from an overdeveloped right lat muscle, significantly reduced the velocity on his fastball.
This spring, the 24-year-old reliever topped out at around 88-91 mph, which was nearly 10 mph lower than his usual velocity. League, who posted a 2.53 ERA out of Toronto's 'pen in 2006, has remained in Florida, where he's been working with a long toss program in an attempt to build up his arm strength.
Thomson update: Toronto right-hander John Thomson, who currently is on the 15-day DL with a shoulder issue, is progressing well, according to Gibbons. Toronto's manager said the club likely will wait until the end of the month to decide what the plan is for the starter, who is rehabbing in Florida.
"I heard today that he's starting to look better," Gibbons said. "When we first told him we were DL-ing him, we told him to go down there and we said we'd evaluate him and see where he was at in a month. We'll see what's going on here and see where he's at."
Overbay sits: Gibbons decided that Thursday was a good time to rest first baseman Lyle Overbay, who is the only pure left-handed hitter in Toronto's lineup. On the mound for the Tigers was left-hander Mike Maroth, the sixth southpaw starter the Jays have faced in their first nine games.
Jason Phillips, who also serves as the backup catcher, started at first base for the Jays and hit ninth. Matt Stairs filled in for Johnson in left field and batted second, which is normally Overbay's spot in the lineup. Right fielder Alex Rios moved into the leadoff spot.
Quotable: "All of his pitches are pretty much above average, so he's going to be a good pitcher. It's something where, from top to bottom, we're going to have to do a good job as hitters and making him work." -- Wells, on Matsuzaka
Coming up: Toronto right-hander Roy Halladay (1-0, 3.46 ERA) will square off against Detroit righty Jeremy Bonderman (0-0, 3.75 ERA) when the Blue Jays host the Tigers at 7:07 p.m. ET on Friday at Rogers Centre.