The Liberty said Ionescu was still under review by a team of physicians but that doctors believe the injury will not require surgery. A Grade 3 sprain is a full tear of the ankle ligament and usually requires months to fully heal. For now Ionescu will work to decrease swelling and increase range of motion over the next few days.
Ionescu rolled her left ankle when she stepped on the foot of Atlanta's Betnijah Laney while bringing the ball upcourt Friday and did not return.
She was sent to a hospital in the Bradenton, Florida, area.
Ionescu was 4-for-5 from the field for 10 points, with one assist and one rebound, before she suffered the injury with 5 minutes, 10 seconds left in the second quarter. Friday marked the third game of her rookie season, and she was coming off a 33-point, 7-rebound, 7-assist performance in Wednesday's loss to Dallas.
The Liberty (0-3) next play Phoenix (1-2) on Sunday (1 p.m. ET, ESPN).
ESPN's Mechelle Voepel contributed to this report.
Sabrina Ionescu helped off after ankle injury
Liberty rookie Sabrina Ionescu drops to the floor after rolling her left ankle and has to be carried off the floor by teammates.