Diggs made the comments Thursday while he was in Nashville for the 2019 NFL Draft.
Cousins was the talk of the 2018 off-season, signing a three-year, $84 million with the Vikings in free agency. That mega-pact was entirely guaranteed. The seven-year veteran responded by completing a career-high 70.1 percent of his throws for 4,298 yards in 16 starts. He also threw a career-high 30 touchdown passes against the just 10 interceptions.
Despite the career-year, detractors doubted Cousins as the Vikings posted an 8-7-1 record and missed the playoffs. Cousins came to the team after journeyman Case Keenum led the team to a 13-3 record and NFC North title. Keenum's Vikings reached the NFC Championship game, before falling to the eventual Super Bowl champion Philadelphia Eagles.
While many quarterbacks around the league get together with pass-catchers on their own time during the off-season to build chemistry, Diggs said that he already has it with Cousins. He said the Vikings just need to keep being consistent in order to get back to the postseason.
"People forget It was his first year," Diggs said. "He hadn't been there for four months and had just gotten there. So as far people being down on him, it's like 'you go play quarterback.'
"He still played well. I haven't given up on Kirk. I think he's going to be a great quarterback. He has the ability do everything because I've seen him do it. I've seen him make every throw. I've seen him come in with a smile each and every single day just because he wants to be better."
Cousins has a great cast of pass-catchers to throw to, including Diggs and two-time Pro Bowl selection Adam Thielen. Thielen is Mr. Reliable. He hasn't missed a game during his five-year NFL career. He also has nearly 300 targets in his last two seasons.
Diggs went off for a career-high 102 catches, 1,021 yards and nine scores in 14 starts in 2018. Minnesota inked Thielen to a four-year, $64 million contract extension earlier this month. Diggs signed a five-year, $72 million pact in July.
A team once known for its fearsome physicality on defense is now terrifying opposing secondaries with its offensive firepower.
But Diggs says critics shouldn't compare the ship sailed by Keenum to that captained by Cousins. He's also moving on from the 2018 Vikings.
"It's kinda crazy because people can't live in the past. They aren't connected at all," Diggs said, while making an appearance at Courtyard by Marriott's Bistro & Banter event.
"It's a brand new league year. We kinda gotta approach it that way. There is no rollover success. I look forward to this upcoming year."
Cousins is cemented as the starter in Minnesota, but Keenum's stance is anything but concrete. He is on yet another journey -- joining his sixth team in eight seasons after being traded to the Washington Redskins in March.
Sources told NFL Network that the Redskins don't view Keenum as the default starter in 2019. Diggs believes his former teammate is still good enough to claim one of the 32 starting quarterback gigs in the league.
But his faith now fully sits with Cousins.
"He is not only just a professional but he really loves what he does," Diggs said. "And it's hard to not like Kirk. If you don't like Kirk, you don't know Kirk. He's going to give you everything he's got. He's going to work his [expletive] off. Just to try to put everybody in position to win. I have faith in him."
Moments from the 2019 NFL Draft