David Riley said he knew that winning a game in the National Invitation Tournament was a big deal for a Big Sky team.

But until Eastern Washington achieved it, he didn’t fully appreciate just how significant the accomplishment was.

“We did some special stuff this season, but I got the most people reaching out to me after this game,” Riley said of the Eagles’ 81-74 win Tuesday over Washington State. “I thought ‘Wow, this is a big deal.’ ”

The victory – which advanced Eastern (23-10 ) to a second-round matchup at Oklahoma State on Sunday – was the program’s first in the NIT. The Eagles’ lone previous appearance in 2003 ended with a first-round loss to Wyoming.

But the NIT victory was also significant for the Big Sky Conference – just the fourth win from the conference and the first since 2002 when Montana State beat Utah State 77-69.

Eastern’s postseason win – the second in program history including a victory over Pepperdine in the 2016 College Basketball Invitational – ended the team’s three-game losing streak, which was capped by an early exit from the Big Sky Tournament.

“We were all down in the dumps since what happened at the (conference) tournament, but I think it was good to take a couple days off and re-energize our mindset,” redshirt sophomore Steele Venters said. “It was just good to go out there (Tuesday) and have fun together.”

Venters, the Big Sky’s MVP this season, led the Eagles with 27 points, his highest total since he scored a season-high 33 on Dec. 3 against North Dakota State.

Now the Eagles turn their focus to Oklahoma State, the No. 1 seed in among the eight teams in this quadrant of the NIT.

It will be the second matchup between the programs, which met previously in the 2004 NCAA Tournament. Oklahoma State won that game 75-56.

This year’s Cowboys finished seventh in the Big 12 standings with an 8-10 conference record and 19-15 overall, which includes their first-round NIT win over Youngstown State on Wednesday.

“They play super hard, super tough,” Venters said. “We’re going to need to rebound, and they play a lot of good defense.”

Riley noted Oklahoma State’s size and athleticism and a style that contrasts with Eastern, which tries to space teams out on defense. The Cowboys lead the Big 12 in rebounding margin at plus-3.5 this season, though their overall field-goal percentage (42.9%) ranks last in the conference.

“We know what we’ve got to do,” Riley said. “It’s a simple game plan, but it’s going to take our best effort of the year to do it for 40 minutes.”

This will be the second Big 12 team the Eagles have played this season. On Dec. 13, Eastern lost to Texas Tech 77-70 in Lubbock. It was the team’s final loss before its 18-game winning streak.

Oklahoma State won both its matchups this season against Texas Tech, which finished ninth in the Big 12 (5-13).

Sunday’s winner will advance to play either No. 2 North Texas or No. 3 Sam Houston in the NIT quarterfinals.