The 31-year-old midfielder recently signed a four-year contract at the Riverside after leaving West Ham in a transfer deal worth £5.5m.
Downing spent eight seasons at Boro after joining as a trainee in 2001 before enjoying spells at Aston Villa and Liverpool before moving to Upton Park two years ago.
Speaking to Sky Sports News HQ, he said: “A bit nervous coming back and excited as well. The season’s just three weeks away. The manager has been really good and I’ve settled in very quickly.
“For me it was a good time to come back. I had two years left at West Ham and there was no talk of an extension. I had a good offer from Middlesbrough, so the security of the contract was good but the pull was my home town club.
“It was also the plans the chairman has and players he was bringing in. I can’t tell you who they are but they are good players.
“I think there’s a really good chance of promotion and I’d like to be part of it. The facilities are first class, which should be a pull for any player.”