The San Francisco 49ers struggled for consistency on offense and had trouble containing Minnesota QB Sam Darnold — a Niner a year ago — en route to losing 23-17 in Minneapolis on Sunday.

OFFENSE: C

The 49ers’ offense played one of its worst quarters of the Kyle Shanahan era in the third Sunday as Brock Purdy (28-for-36, 319 yards) was sacked four times and had as many turnovers as completions — two each. And, yet … S.F. opened the fourth quarter with a 12-play, 99-yard drive to cut its deficit to six. Jordan Mason (20 carries, 100 yards, one TD) proved his Week 1 stand-in for Christian McCaffrey was no fluke, but the play of the offensive line (Purdy was sacked six times and played under frequent pressure), the turnovers and two failed first-half fourth-down conversions were too much to overcome.

DEFENSE: C

Fred Warner (team-high nine tackles, a sack and a forced fumble) was terrific, and this unit kept the 49ers in the game by forcing Minnesota into two first-half field goals — one after Minnesota had 1st-and-goal at the 10. But the 49ers also gave up the longest pass play in franchise history — a 97-yarder from Darnold to Justin Jefferson — and allowed 6.1 yards per rush as the Vikings rolled up 146 yards on the ground. Nick Bosa had two of the 49ers’ four sacks.

SPECIAL TEAMS: D

Mitch Wishnowsky’s first punt was 58 yards — equaling the length of his only one in Week 1 — and then his second was blocked. Jacob Cowing muffed a third-quarter punt, but a turnover was avoided when Isaac Yiadom jumped on the loose ball amid a wild scramble. Jake Moody made a 31-yard field-goal try with 1:12 to play (he’s now 7-for-7) and both extra-point attempts, but a last-gasp onside kick by Wishnowsky was easily covered by Minnesota’s Nick Muse to seal the outcome.

COACHING: C

Three times in the first half, Shanahan went for it on fourth down. It didn’t go well. The 49ers converted the first, but on the second, Shanahan eschewed a chip-shot, game-tying field goal and went for the TD only to have Purdy’s 4th-and-goal pass from the 2 fall incomplete. Shanahan followed that with a 4th-and-2 attempt at the Minnesota 43 that gained only a yard on a Purdy scramble.

OVERALL: C

The 49ers better hope they don’t meet the Vikings in the playoffs — especially on the road. This is eight straight losses in Minnesota for S.F. Mason’s success aside, the play of the offensive line is worrisome. Safe to say the Vikings are not the Jets and the question now becomes: Which is the reality, the cakewalk in Week 1 or the slog in Week 2?framed game