Jayden Daniels has won over the Commanders' fan base with his play so far this year ... and clearly one of the franchise's all-time best players, too -- as Brian Mitchell tells TMZ Sports he's wildly impressed with Washington's new star rookie.

Through five games, Daniels has the Commanders at 4-1 and atop the NFC East ... and Mitchell says it's now apparent to him, the 23-year-old signal-caller's potential is enormous.

"The sky is the limit," the former All-Pro said.

Mitchell -- who co-hosts "B Mitch and Finlay," a DC-area sports talk show -- told us he could see Daniels' maturity from a mile away just after Washington took him with the No. 2 overall pick in the spring's draft ... but he said what really impressed him about the LSU product was the way he maintained his drive even after being named the team's QB1 in the summer.

In fact, the ex-Washington tailback said he's pretty sure if Daniels keeps it up ... a key to the city -- and more -- is in his future.

"If he keeps leading like this," Mitchell said, "he can get this town, this state, this area, everybody around too -- he can feed them from his hands!"

While great so far, Daniels will have a big test on Sunday ... when he and the Commanders take on the Ravens in Baltimore. Mitchell tells us he's expecting a helluva game ... but if his former team should lose it -- he cautioned fans to keep their optimism.

After all, Mitchell explained the whole organization has a different feel to it now that they've got new ownership in addition to a new QB and head coach.