THERE'S an old saying in football that defence is the best form of attack and for the most part of this season Middlesbrough had successfully adopted such a policy.

Without being among the most prolific teams in the Championship, a defensive prowess before the turn of the year provided Boro with the strong base to emerge as genuine promotion contenders.

If hopes of a Premier League return are to remain high, they need to rediscover that steely resolve in keeping the opposition at bay pretty quickly.

A third successive league defeat carried with it the sixth, seventh and eighth goals conceded during that run. It has hardly been the start to 2012 which Middlesbrough fans had been hoping for.

Tony Mowbray has acquired a new striker, Lukas Jutkiewicz, in the hope of strengthening his team's firepower, but the £1.5m man's arrival will count for nothing if Middlesbrough's displays at the other end of the pitch do not improve soon.

Kevin Thomson's sending off seven minutes before half-time at the Ricoh Arena for two clumsy tackles hardly helped. By that time, though, they had already fallen behind to Gary McShefferey's opener.

McShefferey was given far too much freedom to waltz through the visitors' defence to slot beneath goalkeeper Danny Coyne after some nice link up play with Alex Nimely.

That was just a taster of what was to come, as Coventry were able to make the extra man count after the restart to add a further goal from Nimely before the unfortunate Matthew Bates turned a third beyond Coyne to increase the woe.

Having been so tight at the back this season, Mowbray must try to come up with a plan to address the situation, knowing the sudden lapses at the back have coincided with the injury to holding midfielder Nicky Bailey.

And with Bailey's ready-made replacement, Thomson, struggling to get the run of games he requires to find his best after a series of injury problems, Mowbray must attempt to get his players believing again.

“There is a danger in modern day football to over analyse things,” said Mowbray. “Whether it is in papers, on the radio or on TV, football is analysed to a huge extent now.

“What we have to do is concentrate on the football. Train hard, get on with it. The players are fine. They understand we have to be better than we were. Yet had it been 11 v 11 we would have had a decent opportunity to win this game.”

Mowbray had a point and had Scott McDonald or Faris Haroun managed to turn in one of three decent chances in the opening ten minutes then the outcome could have been different.

But the Championship's bottom club Coventry, whose goalkeeper Joe Murphy had to make a fine one handed save to deny Joe Bennett, capitalised nine minutes before half-time through McShefferey.

Then Thomson, initially booked for an earlier challenge on Cyrus Christie that was made worse by the follow through, was issued a second yellow card for leaving his foot in when McShefferey cleared deep inside his own half, which made the struggle harder for Middlesbrough.

Mowbray, who also lost Julio Arca for a two footed lunge on Sammy Clingan late on, said: “I didn't go in to see the referee. I hope he feels he had a poor day. The players out there didn't know what sort of referee he was. All you ask for is consistency.

“You can't appeal yellow cards so we won't be appealing Kevin's and I don't think we will be appealing Julio's either. There's no point in wasting your money. Yet the bottom line is, the ref is not the reason we lost.”

Mowbray felt one of the main reasons for the defeat was Clive Platt. The towering Coventry striker caused problems with his aerial ability, without really testing Coyne himself.

And when the Middlesbrough defence tried hard to keep with Platt for a routine corner, Nimely made most of the space afforded to him by Bennett to direct a header just over the line despite the best efforts of Rhys Williams on the line just before the hour.

Nimely failed to score in ten outings during his loan spell at Middlesbrough, but got off the mark for the Sky Blues on his debut and he was also involved in the third.

He rolled the ball out wide for David Bell and the substitute's cross was miss-hit by Platt on to the leg of Bates and the loose ball bounced beyond Coyne in the Middlesbrough goal.

“Alex did alright. You have got to remember he was playing against ten men for most of the game, so he had more space to get in to,” said Mowbray, who didn't field new signing Jutkiewicz against his old club because of an agreement with counterpart Andy Thorn. “Alex didn't get an opportunity to play in our team, that's life. He moves on and hopefully he will do OK here.”

There was a consolation 22 minutes from time when McDonald turned in Marvin Emnes' centre for his eighth goal of the season. In reality struggling Coventry, who remain six points shy of safety, deserved to end their own slump and Middlesbrough lost this courtesy of some poor defending and a little help from the official.