SANTA CLARA, Calif. — San Francisco 49ers coach Chip Kelly wouldn’t commit to starting Blaine Gabbert new week against Buffalo after a fourth straight loss.

Kelly said Friday the entire offense is on notice after sputtering Thursday night in a 33-21 home loss to the Arizona Cardinals.

“I don’t have any answers for anybody,” Kelly said. “I don’t know who’s going to start against Buffalo. Our entire offense didn’t play well. So, we need to get something straightened out offensively.”

The 49ers are 1-4 and last in the NFC West. Gabbert dropped to 9-31 as a starter, and San Francisco has the NFL’s last-ranked passing offense.

Gabbert threw two interceptions on his own side of the field that led to 10 Arizona points. The Cardinals took advantage of the first to tie it at 7 late in the first half on Larry Fitzgerald’s 21-yard touchdown catch.

“It’s extremely frustrating,” Gabbert said after the game. “I let this team and this organization down tonight and did not play good whatsoever and that’s on me. I had two crucial turnovers there that led to points for the Cardinals and that was the difference in the game right there. I got to do a better job protecting the football and leading this team to scoring more points and winning games.”

Kelly said he will use the time off over the weekend to evaluate his entire offense, which could mean considering a promotion for backup quarterback Colin Kaepernick, who missed the bulk of the offseason program recovering from three surgeries on his left-shoulder, right thumb and left knee.

“He’s continuing to work, continuing to get stronger, continuing to get better,” Kelly said.

The 49ers allowed seven sacks Thursday including a late safety. Gabbert completed 18 of 31 for 162 yards with a touchdown pass and scoring run. He had a 56.1 passer rating.

A bright spot for San Francisco was receiver Jeremy Kerley, who was acquired in a trade with Detroit for offensive lineman Brandon Thomas on Aug. 29. Kerley is the 49ers’ leading receiver with 26 catches for 304 yards and two touchdowns, both coming in the last two weeks.

San Francisco added Kerley after receiver and returner Bruce Ellington was lost for the season with a hamstring injury. Gabbert connected with Kerley on eight of his 18 completions, including five of eight for 75 yards in the first half.

“He’s a dynamic player,” Kelly said. “I think the first thing when you notice Kerls is he can get in and out of cuts very quick. He’s sudden in terms of what he does. He can make people miss. He’s got real good short-area quickness and he’s got outstanding hands. I think he’s, Blaine seems to find a comfort level with him.”

NOTES: Kelly said he’s “hopeful” DT DeForest Buckner can return next week after missing Thursday with a foot injury. … CB Chris Davis left the game in the second half with a knee injury and LB Tank Carradine left with a toe injury. Both were scheduled for MRIs Friday, Kelly said. … LB Aaron Lynch made his season debut Thursday after serving a four-game suspension for violating the NFL’s substance abuse policy. Kelly said: “It was good to have him back. It gave us added depth. So, we’ll see how he continues to grow.”