The injury was caused by irritation when he drags the foot while throwing a pitch. Harrison is flying to Dallas on Monday for an evaluation by an orthopedist.
"I'm just trying to figure something out to get the inflammation to go down," Harrison said. "It's minor. I'm just glad it isn't anything bad."
This is a recurrence of a problem that first emerged last season and was solved with a custom orthotic that was inserted into his shoe. Harrison said the irritation flared up again about two weeks ago for the first time since addressing the problem last season.
The inflammation is not related to a turf toe injury he suffered in 2007, although it is on the same foot. He believes this problem can be solved with a new orthotic insert.
"I need to fix it now during spring training. This way I don't have to worry about it," Harrison said. "If this was the regular season, I'd put anything I had to in there so I could get out there. Right now, I don't need to."
Harrison is expected to rejoin the Rangers in Arizona on Monday night.
Other injury notes:
1B Mitch Moreland is scratched from today's game with a tight right quad.
RHP Kyle McClellan (shoulder soreness) will throw live batting practice Saturday and remains on target to play in Tuesday's game.
RHP Wilmer Font (biceps tendinitis) will throw live batting practice Sunday.
C Eli Whiteside (mild left calf strain) had his calf re-examined Friday. Nothing serious was detected, but he is expected to remain out of the lineup for three to five days.
RHP Neftali Perez (Tommy John surgery) is throwing long toss out to 75 feet.
LHP Martin Perez (fractured left ulna) is not expected to resume a throwing program for approximately four weeks.
Neil Ramirez will replace Matt Harrison as the starter of the split-squad game against San Diego at the Peoria Sports Complex.
Nick Tepesch is starting the home game against Oakland and will throw a spring-high four innings. Tepesch came into camp as an unknown but has pitched well while receiving multiple innings of work in previous appearances. A good performance Saturday could thrust him into the discussion about the open fifth spot in the Rangers' rotation.
Today marks the first of two meetings between Texas and Oakland. The teams will play again at Phoenix Municipal Stadium on Tuesday. Texas and San Diego are playing the second of five meetings scheduled this spring.
With the two games beginning at 2:05 p.m. CT and being played at different ballparks, the Rangers split their staff to attend each contest. Manager Ron Washington will oversee the game against San Diego in Peoria. Bench coach Jackie Moore will lead the team against Oakland. Moore managed the A's from 1984 to '86.
The game against Oakland is the lone home game in a stretch that sees the Rangers play four out of five away from Surprise Stadium.
The Rangers have 154 players in minor league camp after the last group of position players reported Friday. Minor league games begin March 14.
Statistics from Friday's game will not count, as it was canceled after the fourth inning because of rain.