KANSAS CITY, Mo. – End-zone interceptions thrown by Alex Smith were key plays in the most recent Kansas City Chiefs losses, last week against the Tennessee Titans and last month against the Tampa Bay Buccaneers.

Those throws are extreme examples, but for Smith they’re only symptoms of a larger problem. Smith has struggled with passes going into the end zone all season.

Smith has completed 4 of 17 passes he has thrown into the end zone. His completion percentage (24) is second-worst in the NFL, ahead of only rookie Carson Wentz of the Philadelphia Eagles.

Alex Smith ranks among the worst QBs in the league in the red zone this season. AP Photo/Chuck Burton

Smith’s troubles on throws into the end zone can help explain many things. Those misfired passes are reasons the Chiefs are 27th in the NFL in scoring touchdowns from inside the opponent’s 20 (44.4 percent).

They’re also reasons that just 2.8 percent of Smith’s passes go for touchdowns, which is 29th among 31 qualifying quarterbacks. As a comparison, 6.9 percent of Matt Ryan’s passes go for touchdowns for the Atlanta Falcons.

Smith has never thrown a lot of touchdown passes. His career high is 23, set in 2013. But he’s on pace for about 14, which would be a career low for him for a full season.

“The windows are tighter,’’ Smith said, explaining the difficulty of making throws into the confined space of the end zone. “There’s less field to work with. All of a sudden, those 11 guys take up more space as opposed to farther out. Timing is a premium. You’re in a situation where you don’t want to take negative plays or sacks.

“A lot of times, though, you’re shooting through the end zone, shooting through windows and hoping your guy or nobody catches it. The field just gets condensed so everything is now at a premium. Accuracy, timing and everything is at a huge premium in that area of the field.”

League wide this season, NFL quarterbacks complete about 63 percent of their throws. Smith exceeds that, at more than 66 percent.

The league-wide completion percentage drops to 38 for passes into the end zone. That reflects the difficulty of completing such throws. Many times quarterbacks intentionally toss the ball out of bounds or out of the end zone to avoid making a critical mistake.

But some of the league’s best quarterbacks have the best completion percentage in end-zone throws. The top five in completion percentage in such throws: Drew Brees, Andrew Luck, Marcus Mariota, Aaron Rodgers and Tom Brady.

Smith’s company in the bottom six in end-zone completion percentage include not only a rookie in Wentz but three quarterbacks who have been benched by their respective teams (Ryan Fitzpatrick of the Jets, Case Keenum of the Rams and Brock Osweiler of the Texans) as well as Tyrod Taylor of the Bills.

“He’s well aware of how important it is with the ball down there and he’s going to continue to try to fix it as we go,’’ said co-offensive coordinator Matt Nagy, once a quarterback in college and later the Arena League.

“We always say that in the red zone, things happen quicker. When that happens, your progressions happen faster. If he had an extra second [on the interception against the Titans], he would have seen [Travis] Kelce pop open. But the ball is already out. He tried to get one into Jeremy [Maclin] and it didn’t work out. Alex will learn from that. That’s one of his strengths, protecting the football."