The 24-year-old had been laid low since March with a pelvic complaint which caused the right-back to miss the World Cup and the start of the Argentinian's reign in north London.
Walker suffered a setback in September and underwent lower abdominal surgery - a move the north London club had hoped to avoid - but on Thursday he at last made his first-team return.
The England full-back admitted he was a "little rusty" in the 75 minutes he managed in Turkey, but Pochettino was impressed by his display in the 1-0 Europa League defeat to Besiktas.
"I think that he did well," the Spurs head coach said.
"He had a very good performance
He showed that he is fit and we decided only to play him for 75 minutes because it is good for his first official game after his injury
"I am happy
I am happy because he is a very good player and an important player for us."
Walker's return was one of few highlights on a disappointing evening for Spurs at the Ataturk Olimpiyat Stadium.
Pochettino was frustrated by the "laughable" floodlight failures at Besiktas' temporary home, although he was more annoyed by his players' poor showing in front of goal.
Roberto Soldado was the main culprit, with those missed opportunities allowing Cenk Tosun to secure Slaven Bilic's side the victory which saw them go above Tottenham at the top of Group C.
Both sides were already assured of a place in Monday's last-32 draw heading into the match, but the defeat means Spurs, in theory, will now get a tougher draw.
The north Londoners will face a Europa League group winner or one of the best-performing Champions League drop-outs, meaning the mouth-watering prospect of facing Zenit St Petersburg, managed by former Spurs head coach Andre Villas-Boas, is on the cards.
"We need to look forward," Pochettino said
"We have to see the draw on Monday.
"It is a shame because we would have finished top of the table (with a point), but now we need to look forward
"We have to be focused not just on this competition, as we have the Premier League on Sunday and, after, on Wednesday against Newcastle in the Capital One Cup."
"We need to see the draw on Monday and to win the Europa League
It's a shame we didn't finish on the top of the table."
Source : PA
Source: PA