Alan Pardew will almost certainly have to cope without Siem de Jong until December or January as he struggles to win back the hearts and minds of disaffected Newcastle United supporters.

The Holland international has torn a groin muscle in training and is expected to be sidelined for around four months.

As Pardew prepares for games at Southampton on Saturday week and then at home to Hull City seven days later Newcastle’s manager has increased cause to regret his board’s failure to sign at least one more striker before the transfer window’s closure.

Although De Jong is not an out-and-out centre-forward he can operate up front and was a regular scorer for Ajax. Without the Dutchman and with Papiss Cissé still recovering from a broken kneecap, Pardew must now rely on Emmanuel Rivière – struggling to adapt to the Premier League after a £4m move from Monaco – as his principal striker. Cissé is unlikely to return to action until October.

Last month Pardew acknowledged De Jong, troubled by toe and calf complaints in recent weeks, was only about 80% fit and he has started only one Premier League game. During last Saturday’s 3-3 draw with Crystal Palace De Jong appeared to be struggling with the pace, something Newcastle’s manager suspected was a legacy of a previous serious hamstring tear he spent much of last spring recovering from and that effectively ended his season in March.

It will come as little consolation that De Jong passed an exhaustive medical before signing on at St James’ Park and that, although understood to be severe, his groin tear is believed to be completely unrelated to any previous problems.

If attack represents Pardew’s primary cause for concern, Newcastle also have problems in midfield where hamstring trouble once again leaves Cheik Tioté doubtful for the trip to Southampton while Jack Colback is back on Tyneside receiving treatment for a calf injury picked up while on international duty with England.