It seemed as if it were going to be much worse, judging by Cahill's initial reaction.
First baseman Paul Goldschmidt had fielded Jason Kipnis' grounder and flipped to Cahill, who was late in covering first. He fell to the ground after touching the bag and grabbed his right leg.
Head athletic trainer Ken Crenshaw tended to Cahill, who eventually got up and walked down the left-field line to the clubhouse under his own power.
"It was just one of those things where I didn't hear a pop, so I knew it wasn't too bad," Cahill said. "It just felt like a really bad cramp, but I was just kind of scared at first, and then it settled down and started releasing, and I felt like this isn't anything serious. It just kind of went away pretty quick, so I was fortunate."
Cahill's last outing before beginning the regular season is scheduled for Sunday against the Brewers -- after that, he is in line to start the second game of the regular season, March 23 against the Dodgers in Sydney, Australia.
"I have no idea," Cahill said when asked if the injury would prove enough of a setback to interfere with his March 23 start. "It's one of those things, just let it calm down and see how it feels tomorrow."
D-backs manager Kirk Gibson said the initial exam by a doctor showed that things looked good structurally and that the team would re-evaluate it Wednesday.
"It's one of those things we'll find out tomorrow, see how it responds," Gibson said. "He was walking around OK."
Gibson named Cahill as the No. 2 starter in large part because of how he looked during early bullpens and sim games. Since Cactus League games have gotten underway, though, Cahill has not looked as sharp.
In his first start, against the Brewers, he allowed one run on two hits over 3 1/3 innings and seemed to settle in after the first inning.
Against the A's last week, Cahill was hit pretty hard.
Oakland pounded out eight hits and scored six runs against him in just three innings.
On Tuesday before his injury, Cahill again gave up some hard-hit balls and wound up being charged with five runs in 4 2/3 innings.
"Just didn't locate where he wanted to," Gibson said. "Those guys swung the bats well. He was trying to do some things he wasn't able to do. He's throwing the ball fine; we've just got to get his leg to be OK, and he'll be ready to go."
One of the things Cahill tried was to go inside to lefties, which he did with mixed results.
"Still kind of catching too much of the plate," Cahill said. "Last year I felt like fastball command wasn't there. I feel like it's really close right now. I'm missing more on the plate than off the plate, which for right now I'd rather have it like that than be walking guys. I feel a lot better mechanically. I like where I'm at; I've just got to set my sights a little bit farther in or farther out, whatever it may be, especially ahead in the count."