It was reported Tuesday that Baldwin would miss at least two weeks with soreness in his knee, what coach Pete Carroll called "little bit of a problem."
However, on Wednesday Adam Schefter of ESPN reported Baldwin is expected to miss "most, if not all, of the preseason."
According to that report, doctors are "hopeful and confident" that Baldwin will be able to return to the practice field before the start of the regular season.
Baldwin is a major component of the Seahawks' offense.
He was named to the Pro Bowl as an injury replacement after he had a team-leading 75 receptions for 991 yards and eight touchdowns in 2017.
It marked the third consecutive season with at least 75 catches for Baldwin, who set career highs with 94 receptions and 1,128 yards in 2016 while also earning Pro Bowl honors.
The 29-year-old Baldwin emerged as one of the league's top wideouts in 2014 when he had his first 1,000-yard season (1,069) on 78 receptions while establishing a career best with 14 touchdown catches.
An undrafted free agent out of Stanford, Baldwin has spent his first seven seasons with the Seahawks. He has 443 receptions and 44 touchdown catches while starting 77 of 110 games.
Baldwin has appeared in 12 postseason games with Seattle, hauling in 55 catches for 702 yards and six touchdowns.
With Baldwin sidelined, the top receivers for the Seahawks are offseason acquisition Brandon Marshall, Tyler Lockett and Jaron Brown. Second-year wideout David Moore, who was impressive early in camp, also is out with a hip flexor.