Forshaw and Junior Firpo both went off injured, clutching the back of their left legs, in the space of two first half minutes at the London Stadium.
Marcelo Bielsa was forced to replace the senior pair with teenagers making their Premier League debuts in Lewis Bate and Leo Hjelde, but the Whites still managed to pick up a vital 3-2 win in the capital.
Speaking after the game Bielsa said the problems were muscular and the early double substitution was difficult to take.
"Of course, the game being so early on where we had constructed our best moments; to have to generate adaptation with two substitutions always has its cost," said the head coach.
Firpo posted on his Instagram account after the game, saying: "Also, sad about the injury, I will work very hard to come back stronger."
Forshaw has now followed suit, with more encouraging news for Whites supporters.
"Thanks for all the messages, it's only a small hamstring injury," he said.
"I'm fighting to be ready for Saturday, if not I'll be back straight after the break."
The former Brentford and Middlesbrough man spent almost two years out of action through a complex hip injury before returning to Bielsa's side earlier this season and once again becoming a mainstay.
His performances in the middle of the park helped him to build a solid case for a new contract at Elland Road, with his deal due to expire this summer, and on Friday the club confirmed he had put pen to paper on an extension. The new deal will keep him at Leeds until the summer of 2023, but the club have an option for a further year.
The news met favour with Bielsa, who has credited Forshaw for his successful return from injury. The Argentine was not certain Forshaw could come back from such a lengthy absence and be the player that was key to the Leeds team prior to the 2019 injury.
"It is difficult for me to refer myself to Forshaw in this moment where he has given such a valuable response because I didn’t think Forshaw was going to be the player that he was once before, because I don’t want it to seem like the process that Forshaw went through wasn’t with my support," he said.
"He did it by himself with all the support which the club gave him which was a big support but I didn’t participate in his success, I only accompanied him and when the moment came I gave the responses that he deserved to play but the important part of those two years I wasn’t there with him so I don’t want to link myself too much to him because I don’t want to over impose his success. The club would make a very convenient decision if they extended [with] Forshaw because every week he is showing he is a player of a very good level.”