Last Saturday, Purdue was trying to start 15-0 for the first time in school history.
A week later, the Boilermakers are looking to avoid their worst losing streak in nearly four years.
The nation's sixth-ranked team is at risk of a third consecutive loss and an even deeper hole in the Big Ten race when they visit Northwestern.
Purdue (14-2, 2-2) was one of four undefeated teams going into last weekend before losing 73-66 at then-No. 17 Wisconsin on Saturday. The Boilermakers followed that defeat with Tuesday's 70-66 home loss to an Ohio State team which had been 1-3 in league play.
They haven't dropped three in a row since losing five straight to close the 2005-06 season.
Robbie Hummel scored a career-high 35 points Tuesday, hitting eight 3-pointers, and E'Twaun Moore finished with 19, but Purdue was outscored 41-25 in the second half.
The Boilermakers shot 34.5 percent after the break while letting the Buckeyes hit 54.2 percent. Third-leading scorer JaJuan Johnson, averaging 13.6 points, was held to four, and starting guard Chris Kramer played a season-low 15 minutes because of foul trouble, finishing with two points.
"We had some older guys that did not play like juniors and seniors," said coach Matt Painter, whose team was outrebounded for a fifth straight game.
Painter also was frustrated by another poor defensive performance. After forcing a season-low eight turnovers against Wisconsin, Purdue let Ohio State shoot 51.0 percent - no previous opponent was better than 46.0 - and the 32 points scored by Evan Turner were the most by an opposing player since Iowa's Jeff Horner had 32 on Feb. 1, 2006.
The Boilermakers held opponents to an average of 59.8 points in the first 14 games and only one topped 65.
"I liked winning," Painter said. "I liked winning 14 straight games but I don't like the last two games. We've got to do some soul searching and make sure that we understand that defense and rebounding are the two areas that are going to get us to the top of the mountain."
Putting a quick halt to the skid might not be easy. Three of Northwestern's four losses were to ranked teams and the other was in overtime to Big Ten co-leader Illinois, which hosts Purdue on Tuesday.
The Boilermakers, however, have won three in a row in Evanston against the Wildcats.
Northwestern (12-4, 1-3) started the Big Ten season ranked for the first time in 40 years, but it has fallen out of the Top 25 and is 0-2 at home against Big Ten opponents.
The Wildcats lost to then-No. 11 Michigan State on Jan. 2 and 60-50 to No. 13 Wisconsin on Wednesday, when they were outrebounded 38-29 and gave up 15 offensive boards. The Badgers went on a 21-8 run over the final seven minutes to pull away in what had been a close contest.
"I think it was a winnable game," coach Bill Carmody said. "Our guys were disappointed. ... We had to get the ball inside a little more and we just did not do that."
Carmody's team is shooting 37.9 percent in Big Ten play. John Shurna, who averaged 25.6 points on 54.5 percent shooting in five games from Dec. 19-Jan. 7, has scored 26 points and shot 36.0 percent over the last two contests.
Northwestern snapped a five-game losing streak to Purdue with a 64-61 win in West Lafayette on March 4.