Arsenal should be keeping a watchful eye on the Sporting Lisbon v Schalke game this evening.
Arsenal were linked with a move for the player, as an alternative to Sami Khedira. Carvalho, who of course has a release clause in the region of £37.5 million, was heavily linked with Arsenal up until transfer deadline day - but The Gunners did not tie up a deal.
Manchester United were the first team credited with an interest in the player. If David Moyes was still in charge they probably would have snapped him up. However Louis van Gaal was not believed to be as keen on bringing Carvalho to United so the interest died down.
Tonight however could be the performance from William that proves Arsenal need to seriously consider him an option.
Carvalho, who is actually believed to be available for about half his minimum fee release clause, is reportedly set to start at centre-back for Sporting this evening in their Champions League tie with Schalke 04.
According to Portuguese source O Jogo, Carvalho will partner either Mouhamadou-Naby Sarr or Paolo Oliveira at the heart of the Sporting defence this evening - as manager Marco Silva does not want the inexperienced pair alongside each other. Usual starting centre-back Mauricio is suspended.
William's ability to play in the heart of defence has been noted before, but rarely seen. Arsenal not only have problems in the midfield areas, but also at centre-back. For Arsenal in particular this game should make a compelling scouting mission.
The club played Nacho Monreal at centre-back yesterday, with a predictably disastrous outcome, against Anderlecht in a 3-3 draw.
They are also struggling for a genuine holding midfielder. While Chelsea have Nemanja Matic and United have Daley Blind - Arsenal's choices of Mikel Arteta and Mathieu Flamini are struggling for form and fitness.
Arsene Wenger has even openly admitted that a holding midfielder, who can also play at centre-back, would be the ideal target for January.
Tonight very well may be the chance to see that man in action.