Cardinals General Manager John Mozeliak said on the team's Web site an MRI examination was performed to pinpoint the pain in Pujols' back, followed by an injection of anti-inflammatory drugs at the team's spring training facility in Jupiter, Fla.
Mozeliak said the St. Louis star is considered day-to-day.
The injury is the same one that sidelined Pujols for a week earlier this spring. During March, Pujols has appeared in seven of the Cardinals' 18 exhibition contests, during which he has batted .238 average and hit one home run.
Pujols, the two-time reigning National League MVP, hit 47 home runs and drove in 135 last year while batting .327 in 160 games.