After watching Lamb go 0-for-4 in Monday night's opener against the Brewers, D-backs manager Chip Hale called Lamb into his office.
"He saw something and he asked me about it and it's gotten to the point now where I think it's affected my swing and not coming through helping my team," Lamb said. "So we're going to take it day by day and just see how it feels."
No tests have been scheduled as of right now because the team is confident that it is just a bruise.
"Not too worried about it," Lamb said. "Take today, see how it feels tomorrow, but like I said, just day by day."
Hale said Lamb would be available to pinch-hit Tuesday if necessary and that the team hoped to have him back by Friday when the D-backs open a three-game series with the Dodgers in Los Angeles.
In other injury news, ace Zack Greinke (left oblique strain) threw a 40-pitch bullpen session Tuesday in Arizona and is scheduled to pitch in a rehab game Friday. It hasn't been determined for sure yet, but it is expected that the outing will be in the Rookie Arizona League.
Outfielder David Peralta (back) will continue his rehab assignment with Triple-A Reno until he rejoins the D-backs on Friday in Los Angeles.