SANTA CLARA, Calif. — The San Francisco 49ers fear standout linebacker Patrick Willis might have suffered a turf-toe injury in the second quarter of Monday’s win over the St. Louis Rams.

If so, he not only would be unlikely to play Sunday night at the Denver Broncos, but also could miss further action as well.

Willis had x-rays on his left big toe at the stadium Monday night. The 49ers did not announce the results, but they prompted Willis to seek a second opinion Tuesday.

He left the stadium in a walking boot.

The 49ers made no announcement about the injury Tuesday. However, they already have dealt with a turf-toe injury this season, with cornerback Tramaine Brock having missed the last four games after suffering one in Week 2.

The 49ers are expected to announce a course of action for Willis before Wednesday’s practice.

Chris Borland saw his first action of the regular season after Willis left in the second quarter. Borland drew praise from 49ers coach Jim Harbaugh after recording two tackles and breaking up two passes in his relief stint.