Championship leaders Coventry stumbled again as they were held to a 0-0 draw by 10-man Oxford United at the CBS Arena.
Frank Lampard's side have now won just four of their last 13 Championship matches and, having been 10 points clear in December, will drop to second on Monday if second-placed Middlesbrough beat Sheffield United.
The relegation-threatened U's had Will Lankshear sent off in the 77th minute but held on for a valuable draw that leaves them four points from safety.
After surrendering 1-0 leads in both of their last two outings and losing both games, Lampard made five changes including dropping centre-backs Bobby Thomas and Liam Kitching, who were replaced by Joel Latibeaudiere and Luke Woolfenden.
There were also recalls for Haji Wright, Romain Esse and Victor Torp, while Jamie McDonnell replaced Will Vaulks in one of three changes for the U's.
Oxford frustrated their hosts in the opening stages and it took Coventry 10 minutes to register their first shot as Wright's effort was comfortably saved by Jamie Cumming.
Matt Grimes then drove at the Oxford backline, who gave the midfielder time and space to shoot narrowly wide of Cumming's left-hand post.
While Cumming had faced plenty of efforts at the other end, Carl Rushworth made his first save of the afternoon just past the half-hour mark to keep out Ciaron Brown's header.
Tatsuhiro Sakamoto forced Cumming into his latest save when he turned and shot following good work by Esse down the left, and the former Chelsea keeper parried the winger's effort for a corner.
Oxford's last victory came at the home of Coventry's rivals Leicester, and Matt Bloomfield's side had a good chance to go ahead when Christ Makosso played in Przemyslaw Placheta, who opened his body before shooting over.
The visitors almost handed Coventry an opener straight after half-time when Michal Helik intercepted Victor Torp's cut-back from the left and poked the ball straight at Cumming from inside the six-yard box.
Esse then turned Josh Eccles cross goalbound which Cumming had to push to safety before Wright headed a cross from the right wide of the far post.
Coventry's second-half onslaught continued when Esse met a loose ball and drilled his effort goalwards, which was thwarted once again by Cumming.
Makosso was next to save the day for Bloomfield's side when he cleared Esse's rebound off the line after Cumming had made yet another save.
Wright had another chance to head Coventry in front when Torp's wicked free-kick into the box was met by the United States international who guided his effort wide.
Oxford were reduced to 10 men with 13 minutes remaining as Lankshear picked up his second yellow card for barging into Latibeaudiere, just 20 minutes after he had been introduced as a substitute.
Wright came closest to making the extra man count, but he lashed into the side netting as the hosts were forced to settle for a point.
Coventry's Frank Lampard:
"Absolutely one of those days. I thought the players' application was great, the performance was good. Not easy against a low block and organising our distances to play between, but we created enough to win the game and we gave nothing away, maybe one little counter attack first half but yeah, it doesn't go in the net sometimes.
"When you're playing a low block it's not always easy to inject speed and you're not going to play long to three big centre-halves.
"I thought the lads were really balanced in their play in the first half, we wanted a little bit more speed when we could do and we found that straight away in the second half.
"We pushed and pushed, things are hitting them, they're getting blocks in, a couple of chances we might do better and we didn't, but other than that I can't complain with the lads.
"The application was great, they were doing really good stuff on the pitch other than the ball going in the net.
"Could we have stuck it in the box in the last three or four minutes? Yes. Before that did we try and do everything in the right way for me? Yes. Until that we tried everything in the right way."
Oxford's Matt Bloomfield:
"I'm proud of our team, the defensive resilience, the way they we were able to keep fighting against some tough situations.
"The grit, the determination, all the characteristics that we want to see in our team that make us proud of our team and I thought we showed them all today.
"I can't really single anyone out because it was a group effort. Coming to Coventry - what a club, fantastic stadium, top manager, some incredible players for the level - it was always going to be a tough afternoon for us.
"To get a point away from home in any game has to be respected, but to come here and get a point, we have to be so pleased with that."
