Why Chesterfield face mammoth task if they are to upset odds against record-breaking Portsmouth

Town go into the tie top of the table, with just one defeat in 18 in all competitions, including being 13 unbeaten, and winning 11 out of the last 12 in the league. They have racked up an impressive 43 goals in the league – the highest amount in the top five divisions, although the National League has played more rounds of fixtures.

But the Spireites are going to have their hands full on Sunday, up against a Pompey side who are not only top of League One and without a loss in 15 matches in the league this season, but their unbeaten run actually stretches back to March. Their last defeat in League One came against Sheffield Wednesday – 26 games ago – which is their best-ever in their history. Their unbeaten start to this term is the longest in a league season Portsmouth have managed since the end of the Second World War, according to the BBC.

The Fratton Park club are not the highest scorers in League One, but they do have the best defensive record, conceding just 10 times. They also have a deadly finisher in Colby Bishop. The striker has bagged nine goals in 15 appearances this season, leaving him join third in the scoring charts. Not only that,12 different players – the same amount as Chesterfield – have found the back of the net for them this campaign. Another similarity between the two teams is that they both won seven games on the spin earlier this season.

Mousinho, 37, was appointed Portsmouth head coach in January, after leaving his player/coach role at Oxford United. He was described as the ‘standout candidate’, who ‘possesses real leadership and motivational skills’ and has a ‘clear vision.’ On being announced, he said: "I want our team to play on the front-foot, with aggressive and attacking football that will win games and entertain the fans." In total, he has lost just five of his 42 matches in charge. In contract, Blues boss Paul Cook has managed more than 770 games.

Away from home, Pompey have won four and drawn three, but the Spireites are very strong on their own turf, winning seven and drawing one of their eight games at the SMH Group Stadium. As of Wednesday lunch, there were fewer than 850 tickets left on sale in the home areas of the ground.