Walker made five 3-pointers and recorded his 13th career game with 20 or more points. He scored 20 in the second half and moved into 19th at Loyola in career points (1,260).
He was on the assisting end of a dunk by Cam Gregory with 8:02 remaining in the first half that gave Loyola an 18-11 lead, but Jonathan Kasibabu scored on the opposite end for the Stags, starting a 19-3 run to close the half.
Fairfield (2-0) first took the lead, 20-18, on a 3-pointer by Tyler Nelson, but Isaiah Hart responded with a floater in the lane for the Greyhounds (0-2), drawing Loyola even with 3:58 on the clock. That basket, however, was the Greyhounds' final field goal of the half, and they would score just one more point before the break on a free throw by Brent Holcombe.
The Stags took a 30-21 lead into the locker room, and while Andrew Kostecka scored the second half's first points on two free throws for Loyola, Fairfield scored seven of the next nine points to break open a 14-point advantage, 37-23, on a layup by Matija Milin.
Fairfield's lead stretched to 43-26 on a layup and free throw by Kasibabu at 15:08, but it would be Loyola's turn to go on a run.
Walker bookended a layup by Gregory with two 3-pointers, the second coming at 11:58 to make it 43-35 Fairfield. The Stags, however, scored five straight, and Loyola would not get closer than eight for the remainder of the game.
Milin led Fairfield with 18 points and a game-high 11 rebounds, while Kasibabu and Nelson each had 12. Ferron Flavors Jr. added 11 and nine rebounds.
Gregory had seven points and a team-high eight rebounds for Loyola, while James Fives, Kostecka and Hart each scored five.
The Greyhounds open their home schedule Friday at 7 p.m. when they host Towson in Reitz Arena.
Xavier 66, Mount St. Mary's 45: Aaliyah Dunham and Imani Partlow combined for 28 points to lead host Musketeers (2-0) past the Mount (0-2).
Katrice Dickson led Mount St. Mary's with 14 points. She also had a career-high five steals and four rebounds. Ashlee White had eight points, while Caroline Hummell and Bridget Birkhaed had six points each.
For Xavier, Dunham scored a game-high 16 points on 4-for-6 shooting and a 6-for-8 mark from the line, while Partlow added 12 points and seven rebounds. A'riana Gray just missed out on a double double with nine points and 10 rebounds.
The Mount shot just 25.4 percent as a team and 14.3 percent from long range, while Xavier hit 46.2 percent of its shots and had a 27.3 percent mark from 3-point range.
UMBC 72, Gettysburg 45: The host Retrievers (1-2) outscored the Bullets 47-22 in the second half to win. Laura Castaldo had a game-high 18 points for UMBC.
The Retrievers took control in the third quarter after Melody Van Ness scored an and-one to push the lead to four. UMBC ended the third quarter on an 8-2 run, holding Gettysburg (0-1) without a field goal over the final five minutes of the period.
Stephen F. Austin 72, Coppin State 59: The host Ladyjacks (1-1) used a 14-9 run in the second quarter to pull away from the Eagles (0-2).
Coppin State led by six points in the second quarter before falling behind in the closing six minutes of the half. Genesis Lucas had 18 points for the Eagles.
George Mason 80, Loyola Maryland 72: The Patriots (1-1) outscored the host Greyhounds 16-8 in the final six minutes to pull away for the win.
Loyola (1-1) and George Mason were tied 64-64 entering the final six minutes of play until George Mason pulled ahead with a 3-pointer by Sarah Kaminski. The Patriots extended their lead to 71-64 with back-to-back layups before CaLee Gelbaugh's pair of free throws at the 3:53 mark halted their run.