Since his injury-enforced retirement in 2014, Jenas has become the youngest regular pundit on the BBC's Match of the Day programme.
The 33-year-old, who faced Reid on the field several times, has been surprised at his progress.
"From when he first came over to now, I am surprised in his development and how good he is," said Jenas. "It sounds a bit rude to say that but, when he first started, he was a bit raw."
Reid struggled to adapt to the pace and unforgiving nature of the league in his first season at West Ham, before getting a chance to find his feet in the Championship in 2011-12.
"Early on, there were more mistakes in his game," said Jenas. "Now he is fully concentrated for the whole game. You don't see as many mistakes any more, which reassures the whole team. He is now close to the top echelon of defenders in the Premier League."
Reid could become a wanted man. He signed a six-year contract extension in March 2015, ending months of speculation about his future amid reported interest from Tottenham and Arsenal.
"West Ham have done well to keep him," said Jenas. "At one point, it was looking like he was going to leave but that is a testament to the way he's played and developed. He is the rock in that defence and, if he's not there, that's when you have a chance.
"He could probably get into most top sides quite easily. His reading of the game, understanding, pace, strength, agility ... it's impressive. [And] as Winston gets older, he is one of those players who will get better, start to see the game a lot better."
West Ham coach Slaven Bilic agreed, telling the Herald on Sunday earlier this season that Reid's best years were "still to come" and he could "become one of the best".
According to Jenas, the next step for Reid will be maintaining the level that has put him in the spotlight.
"It's about consistency for Winston now. He's reached a level where he has made people stand up and watch, and see what he is about. Now the question is, can he maintain it? Can he continue to do this for another season or two?
"If he can, someone will probably come and take him. Then the question will be, can he do it at the next level which will be Champions League and so on? He could definitely do it.
"West Ham are up there right now but if a big, big team came in for Winston, it would be hard for him to say no."