The oldest and most famous domestic cup competition in world football will continue this weekend as the FA Cup enters its fourth round.

There are a number of tasty ties, including two all-Premier League battles that see Southampton host Crystal Palace and Leicester City travel to face Tottenham Hotspur at White Hart Lane.

However, the magic of the FA Cup lies in its tendency to throw up shock results and, while there weren't a huge number of upsets in the third round, this weekend provides ample opportunity for David to beat Goliath.

Here, Sports Mole looks at five matches in which the underdog will be aiming to claim a famous scalp.

Teams from the lower leagues dream of such ties. Not only is it a money-spinning boost for the club, but the prestige and honour of facing a side like Manchester United is not one such players have many times in their career. Cambridge United, therefore, will be delighted to welcome the Red Devils to Abbey Stadium when the fourth round gets underway tonight.

The U's currently sit 12th in the League Two table but have won their last three matches in all competitions, including a 2-1 victory over Luton Town in the third round. They have also only lost one of their last eight home matches, so will be cautiously optimistic of pulling off one of the most famous results in the club's history. They even have a Manchester United alumnus in their ranks, although Luke Chadwick is a doubt for the match.

As for United, there is a steely determination around the club this season as they look to end an 11-year FA Cup drought. They have lost just one of their last 13 matches and sit fourth in the Premier League table, on course for a Champions League berth. They were given a tricky time by League One strugglers Yeovil Town in the last round until two moments of class from Ander Herrera and Angel di Maria saw them through.

On paper, this one is not a contest. Chelsea have looked unstoppable at times this season and are five points clear at the top of the Premier League table, while Bradford City are only clinging on to the final League One playoff place on goal difference. However, this is the FA Cup, and stranger things have happened.

Jose Mourinho's side were outplayed in midweek as they held on for a 1-1 draw in the first leg of their League Cup semi-final against Liverpool, and with the return fixture to come next week, the hosts are expected to rest a number of players on Saturday. The likes of Diego Costa, Cesc Fabregas and Eden Hazard could sit out, which represents the bulk of their main attacking threat. However, it should also be noted that they have an impeccable record at Stamford Bridge this season, winning 14 and losing none of their 15 outings.

It is a daunting test for Bradford, then, but there are a number of points that could provide cause for optimism. The Bantams have already scored 13 goals in their four FA Cup outings this season, while they made a mockery of the league ladder by beating Millwall 4-0 in their third-round replay. Their run to the final of the League Cup in 2012-13 is also fresh in the memory, during which time they beat three top-flight teams, including Arsenal. They may also take heart from Shrewsbury Town, who ran Chelsea close in the League Cup earlier this season.

Two sides who needed a replay to reach the fourth round face off at Ashton Gate when Bristol City host West Ham United. Two divisions separate the clubs and, while both are doing well in their respective leagues, there is no doubt that the visitors go into the match as heavy favourites to progress.

Yet City will feel that they have as good a chance as anyone of pulling off a shock this weekend. The Robins currently occupy an automatic promotion spot in League One and come into the match on the back of four straight wins and three consecutive clean sheets. That includes victory over Doncaster Rovers in the previous round, with Jay Emmanuel-Thomas scoring both goals in a 2-0 win.

West Ham, meanwhile, returned to winning ways in style at the weekend, ending a run of six games without a victory by beating Hull City 3-0 courtesy of a second-half blitz. They squeezed past Premier League rivals Everton in the last round, eventually emerging victorious following penalties in the replay. It is the first time that the Hammers have reached the fourth round since 2010-11, but with a run of fixtures against top-four rivals such as Liverpool, Manchester United, Southampton and Tottenham Hotspur up next, Sam Allardyce could opt to rest players.

Chris Hughton and his Brighton & Hove Albion side welcome holders Arsenal to the Amex Stadium on Sunday afternoon looking to end the Gunners' defence of their crown at just the second hurdle. The Seagulls were beaten by last season's runners-up Hull in the fifth round of the previous campaign, the same team Arsenal conquered in the third round of the current competition.

Brighton will certainly be more confident of pulling off an upset now than they were perhaps a month ago, with Hughton inspiring an upturn in form since taking over from Sami Hyypia. They have now lost just one of their last seven games, and claimed a hugely impressive 3-2 victory over high-flyers Ipswich Town on Wednesday evening. They remain down in 19th in the Championship table, though.

Arsenal, meanwhile, are once again left with the FA Cup as their most realistic chance of silverware and are looking to become the first side to retain the trophy since Chelsea from 2008-10. They produced a shock result by beating Premier League champions Manchester City at the Etihad Stadium last weekend, making it three consecutive wins without conceding a goal. However, with just one point separating them from the top four and a North London derby with Tottenham on the horizon, Wenger could name a weakened side.

The final match of the FA Cup weekend sees Rochdale host Stoke City at Spotland Stadium, and it is a game that could very well provide an upset to cap the action off. Rochdale have already toppled Championship outfit Nottingham Forest this season, while Stoke needed three late goals to avoid the biggest shock of the third round against non-league side Wrexham.

The Dale go into the match in fine form having won their last three outings in all competitions, including a commanding 4-1 victory over Crawley Town last time out. Promotion is very much on the cards too, with Keith Hill's side currently sitting fifth in the League One standings. They have also only lost one of their last five home outings and will be hoping to create an intimidating atmosphere for the Potters.

Stoke are not the sort of team that are easily flustered, however, and they enter the game in decent form themselves. A 1-0 win over struggling Leicester City at the weekend made it just one defeat in six matches, during which time they have taken points off the likes of Manchester United and Everton. The club reached the final of this competition in 2010-11, and have not been eliminated by a side outside the top division since 2009.