'considered doubtful' is correct and usable in written English.
You can use it when you are expressing doubt or uncertainty about a situation or in a legal context when something is subject to dispute. Example sentence: The authenticity of the document was considered doubtful by the court.
Cornerback JAYRON HOSLEY (hamstring), running back BRANDON JACOBS and defensive tackle SHAUN ROGERS were considered doubtful.
Cornerback Jayron Hosley (hamstring), running back Brandon Jacobs and defensive tackle Shaun Rogers are considered doubtful.
He needed surgery to repair a torn muscle and had been considered doubtful to play again in the series.
It was long considered doubtful whether truly stable orbits could exist near the Lagrangian points of the smaller planets because of gravitational perturbations by the major planets.
It was long considered doubtful whether truly stable orbits could exist near those Lagrangian points because of gravitational perturbations by the major planets.
The backup Matt Hasselbeck is considered doubtful after hurting his throwing shoulder Sunday, and the third-stringer Charlie Whitehurst went on injured reserve Monday with a hamstring problem.
The road to recovery is not complete; Thomas was held out of last Saturday's preseason game and said he considered himself doubtful for Sunday's game.
While Epstein declined to forecast when Martínez might return, Kevin Shea, a team spokesman, said the pitcher would be evaluated on Friday and considered it doubtful that Martínez would start against the Seattle Mariners that night.
A specimen of the nominate population labelled as "Baluchistan" and collected by Richard Meinertzhagen is considered of doubtful provenance.
It was subsequently considered a doubtful species by later Mycena researchers, until a 1999 publication validated the taxon.
Because it was considered "very doubtful whether a chain reaction can be established without separating 235 from the rest of the uranium," Urey began intensive studies of how uranium enrichment might be achieved.
