Seahawks pull to within 23-17

49ers fans suddenly are feeling ill at ease.San Francisco entered Thursday Night Football in a must-win situation at 2-3, losing two division games by blowing second half leads. The 49ers led the Rams 21-7 in the third quarter only to lose 27-24, and they led the Cardinals 23-10 at halftime Sunday only to lose 24-23.The 49ers led 23-3 on Thursday night. They now lead 23-17.Laviska Shenault Jr., who fumbled on a kickoff return in the first half, went 97 yards for a touchdown on a kickoff return, and after the Seahawks forced a San Francisco punt, the Seahawks drove 94 yards in 13 plays. Kenneth Walker ran it in from the 1 with 1:24 remaining in the third quarter.Geno Smith now is 14-of-24 for 187 yards and an interception, and Walker has run for 32 yards on 14 carries.Seahawks cornerback Tre Brown is questionable to return with a hand injury, and the 49ers have ruled out safety Malik Mustapha (ankle).