Manchester United sent a scout to watch FC Porto's 2-0 victory over Moreirense on Saturday amid speculation Louis van Gaal is considering a summer bid for Jackson Martinez.
According to The Express, the Colombian striker - who has also attracted interest from Liverpool - made a positive impression on the Red Devils representative during yesterday's routine win in Moreira de Conegos.
Martinez is currently top of the Primeira Liga goalscoring charts after netting his 16th goal of the 2014/15 campaign, and manager Julen Lopetegui will be determined to keep the 28-year-old at Estádio do Dragao.
However, with a growing list of admirers now keeping a close eye on the South American's progress in Portugal, Porto are resigned to the fact that the £27.5 million rated marksman could leave at the end of the season.
Brendan Rodgers has been mooted as a long-term suitor, but his hopes of luring the talisman to Anfield have now suffered a serious setback following rumours that Manchester United could now make a rival bid.
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Tottenham Hotspur are understood to hold a tentative interest as well, but given the fine form of Harry Kane at White Hart Lane at the moment, Mauricio Pochettino has no need to strengthen that area of his squad.
It all points to Old Trafford being Martinez's most likely destination, although his agent has previously suggested that the player would prefer a move to Italy rather than England.