DES MOINES, Iowa (AP) -- Iowa State once believed that Sam Richardson would solve its long-standing issues at quarterback.
Halfway through a disappointing season, Richardson finds himself fighting simply to remain the starter.
Richardson will keep the job for another week. Iowa State coach Paul Rhoads has named him the No. 1 quarterback ahead of Grant Rohach for Saturday's game against No. 19 Oklahoma State (5-1, 2-1 Big 12).
Richardson and Rohach, a redshirt freshman, were listed as co-starters on a depth chart released Monday. But Rhoads announced Tuesday that Richardson will get the nod against the Cowboys.
''The No. 1 reason is just the knowledge that he has overall, of pre-snap and post-snap,'' Rhoads said. ''Sam's knowledge is just far ahead, quite simply, of where Grant's knowledge is. That's just time and experience.''
Richardson, a redshirt sophomore, has started all six games for the Cyclones (1-5, 0-3) and thrown for 1,255 yards and 10 touchdowns.
But Richardson also has played with an injured ankle since the season opener - and his play has declined over the past few weeks.
Richardson's last two games were the worst of his young career.
Richardson was just 15 of 38 passing in a loss at Texas Tech. Last week, Richardson was 7 of 14 for 68 yards and an interception as the Cyclones were trounced 71-7 by Baylor.
It got so bad in Waco that Rhoads went to Rohach for the first time.
Rohach was 8 of 13 passing for 65 yards, with a touchdown pass and an interception against Baylor's reserves. But Richardson was able to keep from further exacerbating his ankle injury, which helped him hold onto the job for another week.
''We plan on him playing at a higher level with his physical health. He's got to make smarter decisions and quicker judgments,'' Rhoads said.