KANSAS CITY, Mo. – It was the 49ers’ first preseason game, but it started by looking just like their injury- and loss-filled 2016 season.
The 49ers kicked off the Kyle Shanahan era by initially getting kicked in the teeth Friday night in a 27-17 win over the Chiefs at Arrowhead Stadium.
The first play of scrimmage? Cornerback Rashard Robinson was burned for a 32-yard completion to set the stage for a 75-yard touchdown drive that ended seven plays later. That was enough for quarterback Alex Smith and most of Kansas City’s starters, who took the rest of night off.
Meanwhile, the 49ers’ only two drives with their offensive starters were unsightly. The totals: zero first downs, three yards, an illegal-formation penalty and a forgettable stat line (1 of 4, 3 yards) for quarterback Brian Hoyer.
Oh, right, it got even worse for a team coming off a 2-14 season: defensive tackle DeForest Buckner left the game on the first drive and was immediately declared out.
The good news: Buckner’s injury didn’t appear serious and – say it all together — it was the first preseason game.
That is, Shanahan and company still have plenty of time to clean up the messes after a game in which they committed 17 penalties (131 yards) and had a field-goal attempt and a punt blocked.
How ugly was it? The 49ers made so many mistakes that, by halftime, it was a blur to Shanahan. In the second quarter, the 49ers had an eight-yard touchdown pass from Matt Barkley to Aldrick Robinson wiped out by penalty. Still, Shanahan incorrectly said the 49ers had two scores nullified.
“We’ve got to clean up the penalties; anytime you get in the end zone twice and neither of them count,” Shananah said on KPIX-TV at halftime. “… We’ve got to clean that stuff up.”
It’s likely that few will recall what happened Friday night by September, but the first few minutes did nothing to dispel doubts surrounding two positions: cornerback and quarterback.
Robinson is the No. 1 corner and the other spot will likely be filled by either Keith Reaser or Dontae Johnson, both of whom are unproven.
On Friday, Robinson, a 2016 fourth-round pick, didn’t look up to the task of being the leading man.
First, he was beaten badly down the right sideline by wide receiver Tyreek Hill on the game’s first play for the 32-yard gain. Six plays later, he whiffed on an open-field, third-down tackle that would have prevented a first down. On the next series, he surrendered an 83-yard touchdown to Chris Conley, although it was nullified by Conley’s pass-interference penalty. Two plays later, he was in coverage again on a 29-yard pass to Conely.
Robinson’s nightmare was finally interrupted when he intercepted a short pass floated by Tyler Bray, who threw the errant ball when he was pressured by rookie defensive tackle Solomon Thomas.
On offense, Hoyer, who is hoping to prove he’s a capable starting QB, had a forgettable six-snap debut with the 49ers. He did zip a 15-yard over-the-middle completion to fully outstretched Jeremy Kerley, but it was wiped out by an illegal-formation penalty.
“You’d like to go out and have a little bit more success,” Hoyer said. “But I think it was good to get out and play against a different team and see what we need to work on.”
Eric Branch is a San Francisco Chronicle staff writer. Email: EBranch@sfchronicle.com Twitter: @Eric_Branch