Swansea City are enjoying the playmaker's fine form, as useful as the defender has been in exchange for Tottenham.
Indeed, the pundit feels Sigurdsson is a 'brilliant' player and was heaping praise on the 26-year-old after another good performance for the Swans over the weekend.
And Hartson told BBC's Final Score on Saturday afternoon: "Sigurdsson is a technically brilliant player. £10 million Spurs paid for Davies - plus Sigurdsson. What a piece of business from Swansea."
Davies, of course, has done well at Spurs, while the forwards currently at White Hart Lane have all contributed to a phenomenal season for Tottenham.
That said, there are Erik Lamela critics out there and they may have preferred keeping the Iceland international on board and starting him instead of the Argentine.
In truth, both Tottenham and Sigurdsson have done well since the move, so it has worked out for both parties. Swansea look safe despite defeat to Bournemouth on Saturday afternoon and Spurs are still going for the title.