[football] direct news understands that Manchester United and Chelsea are the only two teams remaining in the race for Porto striker Jackson Martinez. The Colombian striker has been in superb form this season, contributing to Porto’s season with an impressive 19 goals and three assists in 27 games. Numerous big spending European clubs have been credited with interest this season after watching the 27-year-old but it is understood that only Manchester United and Chelsea remain. Inter Milan, Borussia Dortmund and Atletico Madrid had all sent scouts over to Portugal to cast an eye on the striker but have become discouraged by his 33.2m release fee, something United and Chelsea seem capable and willing to pay this summer. Both Premier League clubs are desperate to improve their attacking options this summer, yet Chelsea could steal the march if United are successful with their enquiries over PSG striker Edinson Cavani. Should Martinez leave Porto, he would follow suit to a number of high profile strikers who have excelled at the Portuguese club and moved on, none more famous than Radamel Falcao.