Firpo featured in United's first two league games of the new season but that was then hit by coronavirus and afterwards suffered a muscular injury upon returning to the side.
After missing five games, the left back returned to the team as a second-half substitute in this month's 2-1 defeat at Tottenham Hotspur and was then back in the starting XI for Saturday evening's clash at Brighton.
What is happening to former Leeds United star Raphinha at Barcelona amid latest farce and deadline
Leeds United plot ‘double hit’ for attacking duo, Whites ‘weighing up’ bargain defender swoop
Leeds United news: Raphinha set to miss La Liga opener as Whites eye MLS left-back
Leeds United ‘express interest’ in transfer as ‘decision made’ over player’s future
Leeds United in ‘direct talks’ over swoop for rising star as Jesse Marsch makes ‘transfer decision’
The defender endured a torrid return to the side facing Brighton's Tariq Lamptey, Firpo booked for fouling the right wing back after five minutes and then taken off at half-time.
Bielsa, though, has provided a positive update about the progress of the Dominican Republic-born player ahead of Tuesday night's clash against Crystal Palace at Elland Road.
“Junior is a player that is growing as he puts minutes together," said Biela.
"His performances have been improving until he had an interruption due to injury and now he is progressively recovering his best form as it happened like so at the beginning of the season.
"The last game was a difficult game for us down the right sector of the opponent, he suffered a caution early on and that conditions the player with the freedom that he has to go and win the ball and the coordination down the left did not give him the back up that he would usually have.”
A message from the Editor:
Leeds has a fantastic story to tell - and the Yorkshire Evening Post has been rooted firmly at the heart of telling the stories of our city since 1890.
We believe in ourselves and hope you believe in us too. We need your support to help ensure we can continue to be at the heart of life in Leeds.
Subscribe to our website and enjoy unlimited access to local news and information online and on our app.
With a digital subscription, you can read more than 5 articles, see fewer ads, enjoy faster load times, and get access to exclusive newsletters and content.
Click here to subscribe.
For more details on our newspaper subscription offers click here.
Thank you Laura Collins