Executive director (football) Dennis Wise – who failed to sign a left-back for former manager Kevin Keegan in the summer – sent scouts Jeff Vetere and Lil Fucillo to Ewood Park on Saturday to see Blackburn Rovers take on Sunderland.

And the pair were understood to be watching England international Warnock, heavily linked with a move to St James's Park during the last transfer window.

Left-back has long been a problem position for Newcastle, and Keegan had said at the end of last season that it was the one position, above all others, he wanted to strengthen, with Jose Enrique – signed last year from Villarreal for a reported £6.3m – needing competition.

However, Wise, to the frustration of Keegan, did not sign a full-back, and Enrique's abject performance in Saturday's 2-2 home draw against Wigan Athletic laid bare the necessity to add a left-back to the squad in January's transfer window if United are to pull out of relegation trouble.

Still, the question remains will Wise be given money to go out an sign a top-level player like Warnock should the club still be in Mike Ashley's hands at the turn of the year.

Rovers boss Paul Ince, who fought off interest from United after taking charge, does not want to lose any of his key players, and it would take a sizeable bid to prise the 26-year-old away from Ewood Park.

And Newcastle could face competition from Manchester City manager Mark Hughes, who signed Warnock for Blackburn in January 2007 from Liverpool.

In any case, Warnock, said to have been keen on a move to United in the summer, might now have reservations about such a switch with so much uncertainty at St James's Park as the club is still for sale and interim manager Joe Kinnear remains on a month-to-month contract.

Midfielder Charles N'Zogbia and centre half Sebastien Bassong have also been deployed at left-back this season, but neither is seen as the solution to the problem.