Manchester City 0-2 Middlesbrough

• On-loan Chelsea striker Bamford opens scoring

• Pellegrini's side beaten on return from Abu Dhabi

• City went out to Championship Wigan last season

• Boro keep sixth clean sheet in seven games

Manchester City were knocked out of the FA Cup by Championship opponents for the second season running as they were shocked at home by Middlesbrough.

Middlesbrough striker Patrick Bamford, on loan from Chelsea, bundled in the first after an error by Fernando.

Lee Tomlin hit a post for Boro, while Frank Lampard did the same for City.

But substitute Kike struck a second on the break for the visitors, who followed Wigan's example of last season by knocking City out of the cup.

Manuel Pellegrini's side, who returned from a five-day warm-weather training trip to Abu Dhabi on Friday evening, faded badly in the second half against a side who thoroughly deserved their victory.

Middlesbrough, with the Championship's best defensive record, needed to be resolute in the face of intense first-half pressure, before creating a host of chances themselves in the second.

Tomlin had an early goal rightly ruled out for offside against Bamford in the build-up, but the visitors were thankful to goalkeeper Tomas Mejias - in for the rested Dimi Konstantopoulos - for six excellent first-half saves.

Mejias, who was part of Pellegrini's squad at Real Madrid, denied Aleksandar Kolarov, Stevan Jovetic twice, James Milner and David Silva in the final 20 minutes of the first half.

Perhaps the best of those saves was a dive to his right to push aside Silva's deflected shot nine minutes before half-time.

Boro got lucky in the midst of all those chances as Dedryck Boyota blasted over from six yards, and might have conceded a penalty when Daniel Ayala handled inside the area to halt Kolarov's progress, but referee Phil Dowd gave nothing.

And the visitors rode that fortune to take the lead early in the second half as City's defending went to pieces.

A Fernando back pass fell short, allowing Albert Adomah to tackle the ball beyond keeper Willy Caballero, and the Brazilian's attempted clearance as it rolled towards the line rebounded in off Bamford.

Middlesbrough then passed up five excellent openings to extend that lead, the first two of which ended with Caballero recovering from his own dreadful clearance to stop Tomlin and Grant Leadbitter with a double save.

Adomah failed with an attempted lob over the goalkeeper after a terrific crossfield pass from the impressive Tomlin, who hit the post moments later following a beautiful drag-back turn, before Caballero palmed out a Jelle Vossen volley.

Lampard, on as a substitute, might have earned a replay with a deflected curling shot that struck the inside of the post.

That would have been harsh on Boro, who secured victory when Adomah broke away and combined with Bamford, feeding Kike to fire past Caballero.

Manchester City manager Manuel Pellegrini said: "Before they scored the first goal, we had five or six clear chances and they didn't have one. But we conceded a very easy goal, and the game changed. They are a team who work well; that's why they are second in the Championship. They had opportunities to score more goals and deserved to go through.

"I wanted to continue in all the competitions but now we must focus on the Premier League and Champions League. We now have a difficult game against Chelsea. We must reduce the five-point gap."

Asked if he thought City's trip to Abu Dhabi had tired them out, he replied: "No, I don't think so. It's easy to have an excuse, but I don't think that was the case."

Middlesbrough manager Aitor Karanka said: "I'm proud of the players, the crowd, the fans, the staff and the club. Manchester City had a lot of chances to score in the first half and I was concerned, because they have a lot of quality.

"They always have an attacking threat, and it was our third game in a week. We could have won by more because we were very well organised and have quality up front.

"At half-time I told my players - and maybe they thought I was crazy - 'Manchester City are in our hands because the only chances they had in the first half came from our mistakes.' We didn't lose the ball like we did in the first half and that is why we had this chance."

Aitor Karanka was part of Jose Mourinho's coaching staff that replaced Manuel Pellegrini at Real Madrid in 2010

Lee Tomlin's header into the net was disallowed for offside against Patrick Bamford

Bamford, on loan from Chelsea, scored his second goal in two games

Stevan Jovetic was denied twice by Tomas Mejias before half-time