Hull are 17th in the Premier League, a place and two-points above the Swans with six games still to play.
Ricketts says Hull's momentum began they day they beat Swansea in March, who have since slumped
"Up until then, since [manager] Paul Clement came in, they were fantastic," Ricketts told BBC Wales Sport.
He continued: "I thought Swansea were going to stay up. I went to the Hull v Swansea game thinking Swansea, who had just had a fantastic win over Burnley, just needed to come up to Hull and not lose and they would have been safe.
"But Hull won that game and from then, they have been winning and have the momentum. They have a two point advantage at the minute so I am afraid to say, with my Swansea hat on, I think Hull are favourites at the moment to stay up."
After an initial upturn in form when Paul Clement replaced Bob Bradley at the turn of the year, Swansea are without a win in their last five Premier League games and struggling for form.
"Ultimately I think this has been coming for two years, ever since Garry Monk had that fantastic year where Swansea over-achieved and had their highest finish ever in Premier League," Ricketts added.
"I don't think the club took on from that, progressed and invested in new players and really tried to strive and push forward.
"No-one wants to see it happen, but if they do go down, re-form and come back a stronger side then it's not the end of the world.
"But ideally you stay up and Paul Clement can do that [re-build] anyway in the summer."
Former Swansea City and Hull City defender Sam Ricketts says the Welsh club are favourites to be relegated of the two this season.