Manning enjoyed the finest season of his glittering career in the 2013 campaign, throwing a record 55 touchdowns and 5,477 passing yards on the way to an unprecedented fifth MVP award.
However, it ended in disappointment as he threw two interceptions in the Super Bowl in which the Broncos were thumped 43-8 by the Seattle Seahawks, leading some to question whether the match would tarnish the 37-year-old's legacy.
However, Welker believes that his career is far from over and insists that he is on his way up as a player despite his age.
"He had the best year of his whole career at 37, so I wouldn't say he's slowing down. He's going upward, not downward," Welker told reporters.
The defeat leaves Manning with a 1-2 record in Super Bowls and an 11-12 record overall in the playoffs.