Haidara has not featured for Newcastle since the 6-2 Premier League victory over Norwich last October after suffering meniscus injuries to his knee.
But the French full-back played 45 minutes for the U23 side in their 1-1 draw with Stoke on Monday night.
"It's been a long, long time," Haidara told nufc.co.uk.
"My last game was in October last year, so I'm really happy.
"I just played 45 minutes and I felt good.
"It's been a lot of hard work for eight months. I worked hard, and now I'm just enjoying playing. I'll take it step by step until I'm fit for the first team."
Haidara moved to Tyneside from Nancy for £2m in August 2013 and has made 49 appearances for the Sky Bet Championship club.
The 23-year-old expects to build up his fitness further in other U23 games before trying to force his way into Rafael Benitez's senior side.
"I felt alright. I could have done more, but with the staff we decided I would only play 45 minutes," Haidara said.
"It's just about building it up - I don't want to go too quick, so I just played 45 minutes and next time I will play more.
"You don't feel strange, but you have to do everything like before.
"It was okay - I wasn't too lost, just maybe in the first 10 minutes I was a little bit tired, but after that I was fine. This has been very good for me."