Big East tournament seeds and NCAA Tournament positioning are on the line when Creighton visits Xavier in a pivotal Big East matchup Saturday in Cincinnati.Creighton (20-8, 13-4) wants to stay one game ahead of third-place Marquette in the conference with one week remaining. As for catching first-place St. John’s, the Bluejays would have to win their final three games and the Red Storm would need to lose their final two to tie for the regular-season title.The Bluejays are coming off a 75-65 home win over last-place DePaul on Wednesday in Omaha that underwhelmed their head coach.”Thirteen turnovers, unacceptable. Fifty percent from the field, basically, in the second half by DePaul is not acceptable,” Greg McDermott said. “We’re going to have to be better. We’re going to go into a hornet’s nest on Saturday and if we think this is good enough, we’re kidding ourselves.”Creighton continues to be led by fifth-year star Ryan Kalkbrenner (18.9 ppg, 8.7 rpg, 2.7 bpg) while point guard Steven Ashworth averages 17.0 points and 6.9 assists.Xavier (18-10, 10-7) has won a season-best four straight in Big East play and stands 13-2 at home. Not only are the Musketeers trying to remain in the top five of the Big East standings to ensure a conference tournament first-round bye, they are also trying to improve their resume for an NCAA at-large bid.