"The [Cousins] to [Demaryius Thomas] and myself combination would be dangerous!!" Sanders said Tuesday on Twitter.
Sanders, 30, was limited to just 47 receptions for 555 yards and two touchdowns as the Broncos used a quarterback carousel last season. In 2017, Trevor Siemian, Brock Osweiler and Paxton Lynch combined to complete just 58.7 percent of their passes for 3,668 yards with 19 touchdowns and 22 interceptions for a 73.0 passer rating.
Lynch is under contract and 2017 seventh-round selection Chad Kelly, who is the nephew of Pro Football Hall of Famer Jim Kelly, is also on Denver's roster.
Broncos president of football operations John Elway said at the NFL Scouting Combine last week that the team had the salary-cap flexibility to do any deal and would consider any quarterback on the open market.
"I think we're going to explore all options in free agency and see where that goes," Elway said at the time. "Obviously we've got the fifth pick in the draft, too. That will all play into it. We'll continue to look at all of the options out there when it comes to quarterback."
Cousins, who has played two seasons for the Washington Redskins on a franchise tag, topped the 4,000-yard mark for the third straight year in 2017. He finished with 4,093 yards, 27 touchdowns and 13 interceptions.
The 29-year-old's time in Washington is running short, however, after the Redskins agreed to a deal with fellow quarterback Alex Smith on Jan. 30.
That deal can become official on March 14, the first day of the new league year. Cousins will become a free agent on that day as well.