A definitive timeframe for recovery is yet to be set for the Northern Irishman due to the severity of the injury which saw him stretchered off last Saturday.
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The 31-year-old has undergone surgery and already vowed to return 'stronger than ever', but faces a long road ahead.
Consequently, Leeds' summer transfer priorities will be expected to shift somewhat.
Dallas has featured in each of Leeds' Premier League fixtures since the club's top flight comeback two years ago and will leave a considerable hole in the first-team.
Part of the reason for Dallas' longevity in the side has been his versatility across multiple positions.
Due to the size of Leeds' squad, Dallas has been the head coach's go-to deputy in several areas of the pitch, standing in for Luke Ayling, Junior Firpo, Mateusz Klich and Adam Forshaw whenever needed.
His absence over the coming months will leave Leeds short in not one, but multiple areas.
A solution to this will likely come in the transfer market, but finding a replacement - temporary or otherwise - for Dallas, is an additional transfer objective for the club this summer.
Bielsa had previously explained why Leeds were unable to spend large sums on first-team-ready players in previous windows, opining that that calibre of player costs in the region of '£20-£30 million'.
"In reference to the amount of players that we have in the squad, it is not only about the amount of players but the quality of the players that are for the squad," he said last November.
"So the players will have the level for any position, it would cost us a minimum between 20 and 30 million pounds."
Assuming Leeds now need to cover multiple positions while Dallas is unavailable, this is likely to cost as Bielsa predicted.
"To give an example, if the club had to replace Bamford, what amount should they invest? A winger costs £30-40 million, how much does a centre-forward that scores goals cost?" Bielsa said in January this year, further stressing the financial constraints clubs such as Leeds must contend with.