Mason Greenwood put United ahead with a low strike but 16-year-old Luke Matheson smashed home a famous equaliser 14 minutes from time for League One Rochdale to force penalties.

Jimmy Keohane was the only player who failed to score in the shootout, with Sergio Romero saving his effort and United scoring all five efforts.

While the hosts, who had 31 shots during the 90 minutes, left the pitch rather sheepishly, Rochdale earned a standing ovation from the 5,500 travelling supporters.

United travel to Chelsea in the fourth round in the week commencing 28 October.

Last month, the biggest date in Matheson's diary was to collect his GCSE results from Trinity C of E High School in Fallowfield. He got 10 in all, including an 8 in PE, more than enough to allow him to enrol for the A-Level courses he feels will be beneficial if his football career does not work out.

School is less than five miles from the world famous arena Matheson shook to its core with the first goal of his 14-match professional career.

United thought they had freed themselves from Rochdale's grasp through Greenwood's low drive.

But a team who conceded six at Peterborough and have been beaten by Manchester City Under-21s this season proved more difficult to get rid of than United imagined.

Eight minutes after Greenwood's goal, Matheson drove a volley into the ground after advancing into the box and sent it bouncing over Romero.

Matheson, who became the youngest player in Rochdale's history when he made his first-team debut 12 months ago, was mobbed by ecstatic team-mates.

United's efforts to regain the lead met with the same disappointment felt when Paul Pogba headed their best chance over in the first half and Marcos Rojo sent three long-range shots way off target.

Yet even the relief at a win came with a sting for manager Ole Gunnar Solskjaer, whose ailing side face a tougher test in the next round.

Too many players failing to deliver

This has not been an easy few days for United. Beaten at West Ham on Sunday with a performance condemned on TV by former skipper Roy Keane and former manager Jose Mourinho, Solskjaer is a man under pressure.

Executive vice-chairman Ed Woodward tried to help on Tuesday when, instead of concentrating of record financial turnover of £627m, he spoke of a club "resolute" in their desire to return to former glories.

In addition, Woodward called for Solskjaer to be afforded some patience by a demanding supporter base.

It is understood these sentiments have been reinforced even more forcefully in private.

Senior figures are adamant the club is on a long-term path and will not be deflected from it no matter what short-term difficulties may arise - and there is an acknowledgement some tough days probably lay ahead before the current campaign is done.

This is a laudable stance to take, in keeping with a club that had two managers - Sir Matt Busby and Sir Alex Ferguson - who were in charge for well over 20 years.

However, in an era where Newcastle can demand £50m for a 21-year-old midfielder with barely any first-team experience in Sean Longstaff and simply end negotiations when United baulked at the fee, the Old Trafford rebuilding job is going to be long and expensive and comes with absolutely no guarantee of success.

Solskjaer is not making a particularly convincing job of making fans believe better times are on the horizon.

There were positives against Rochdale but they were mainly through the youth of Greenwood, scoring for the second time this season, and 19-year-old defender Brandon Williams, who was introduced for his debut at half-time.

But too many experienced players are failing to deliver and Monday's Premier League encounter with Arsenal does not promise much in the way of a change in fortune.

'Learning curve for United'

Manchester United boss Ole Gunnar Solskjaer: "Go 1-0 up, get the second. That is a learning curve. At this club you don't just sit back and think one is enough.

"Mason Greenwood has two great feet. He's a nightmare for defenders; he can go both ways. He is young. We will allow him to grow slowly but surely.

"The players wanted to take the penalties. I am very pleased with the confidence. [We are] better in penalty shootouts than in proper games."

On the fourth-round tie with Chelsea: "If you want to win, you have to beat the best. It slots nicely into a couple of weeks with loads of travelling. We are going to relish it."