"Just a little tweak; little strain," head coach Frank Reich said, according to Andrew Walker of Colts.com. "So my whole mode - and our whole mode - is going to be during this session just to be real conservative with anybody who has any issue whatsoever.
"Where we're at right now is we'll just say, 'Hey, play conservative this week. Nothing this week, and then we'll re-evaluate it after this week and see where he is.'"
The Colts' OTAs are scheduled over the next three weeks.
Luck, the 2018 NFL Comeback Player of the Year, missed the 2017 campaign with a shoulder injury. There's no indication his calf ailment could linger long term.
Luck threw for 4,493 yards with 39 touchdowns and 15 interceptions last year, helping Indianapolis return to the postseason for the first time since 2014.