West Ham United's woes intensified as the Premier League club were thrashed 5-0 in the FA Cup by second tier Nottingham Forest with Jamie Paterson netting a hat-trick in a humiliating third-round rout on Sunday.

The wheels came off in spectacular fashion for West Ham in a result that heaps more pressure on boss Sam Allardyce who made nine changes to his starting line-up with one eye on the first leg of their League Cup semi-final at Manchester City on Wednesday.

Chelsea showed their fellow Londoners how to negotiate a potentially tricky Cup tie in the east Midlands, winning 2-0 at second tier Derby County, with second half goals from John Obi Mikel and Oscar while Sunderland also came through 3-1 against Carlisle.

West Ham, 19th in the top flight and facing a relegation battle, were undone by a Forest side who scored early in the first half with a cheeky Djamel Abdoun penalty before Paterson netted three times in the second half and Andy Reid added a fifth.

There were rows of empty seats at Forest's City Ground, but the fans who had made the trip were treated to a comprehensive victory with the wheels set in motion after 12 minutes when Paterson was tripped in the area by George Moncur.

Abdoun finished with an audacious chipped penalty to put the hosts ahead and Paterson doubled the lead after 65 minutes with a low finish across the keeper for the twice European champions.

Paterson, who had not scored since joining Forest from Walsall in the close season, grabbed his second with another first-time, low finish after 71 and added his third with a well-taken effort on 79.

Reid poured embarrassment on the visitors with a rifled finish into the top corner in injury time.

Forest's local rivals Derby had little joy against Chelsea, who named a strong side that had enough class to dominate their lower league opponents.

Mikel put them ahead after 66 minutes, the Nigeria international getting on the end of a Willian set-piece to head in his fourth goal for Chelsea in almost 300 appearances.

Oscar added a second from the edge of the area to make the game safe and set up a fourth round tie at home to Premier League Stoke City.

Sunderland were briefly made to sweat when Adam Johnson's opener was cancelled out by Matty Robson just before halftime.

The second half was just five minutes old however, when a comical own goal restored the Premier League side's lead, with Sean O'Hanlon sliding in to divert Johnson's cross into the net.

El Hadji Ba made the game safe on 90 minutes when he sidefooted home from close range.

"Mikel plays in an intelligent and safe way, and there was a smile on my face when he scored. It was like a winning goal," Chelsea boss Jose Mourinho said after the match.

Liverpool play Oldham Athletic and Manchester United take on Swansea City in later Cup games on Sunday.

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