The Vikings, the NFL’s lone undefeated team, will spend their bye week evaluating both internal and external options up front after yet losing another offensive lineman.

Coach Mike Zimmer announced Monday that right tackle Andre Smith, who sat out Sunday’s 31-13 victory over the Houston Texans because of a triceps injury, will have surgery on Tuesday. Smith will be placed on injured reserve and is likely done for the season.

Smith is their second starting bookend to go down in the season’s first five weeks. Left tackle Matt Kalil is also on injured reserve after undergoing hip surgery in Week 3.

The Vikings are down to a pair of reserves, T.J. Clemmings and Jeremiah Sirles, at left tackle. But Zimmer said the team will consider signing a veteran free agent. He added that Jake Long, a four-time Pro Bowl selection, worked out at Winter Park on Monday. Zimmer would not say, though, whether the Vikings planned to offer him a contract.

“I don’t know. We’ll see,” Zimmer said. “If we sign somebody, we’ll let you know.”

Long was the first overall pick in the 2008 draft by the Miami Dolphins. Their first-year coach that season was Tony Sparano, now the Vikings offensive line coach. Long played well in Miami before injuries derailed his career.

The 31-year-old has dealt with back and biceps injuries along with a pair of torn anterior cruciate ligaments in his right knee. After stints in St. Louis and Atlanta, Long agreed this summer to a one-year contract in Baltimore. But when the Ravens, concerned about the condition of his knee, insisted Long sign an injury waiver, he balked and the deal fell through.

While Smith, another injury-riddled, former top-10 pick, struggled in his first three starts before getting injured in the first quarter of the Vikings’ Week 4 victory over the New York Giants, his absence leaves yet another void on an offensive depth chart that has been beset by injuries.

After their offensive line was again a major liability in 2015, the Vikings signed Smith and left guard Alex Boone in free agency and vowed to encourage competition at every offensive line position other than the one Boone would occupy. By the time this summer rolled around, though, most position battles did not materialize.

The Vikings entered spring workouts with nine linemen who have started 16 NFL games. Now they are down to four.

Right tackle Phil Loadholt, while far from a lock to make the team, retired before the start of training camp after suffering another leg injury. Center John Sullivan, after being idle for the entire 2015 regular season due to a pair of back surgeries, did not look like himself when the pads started to pop this summer. And Mike Harris, who has started for the Vikings at both guard and tackle, has been sidelined due to an undisclosed illness.

Zimmer said Monday that he does not expect Harris to be cleared to return this season. He did not provide an update on right guard Brandon Fusco, who is going through the league’s concussion protocol after suffering a brain injury in the first quarter Sunday.

Zimmer acknowledged, though, that blocking has been a problem for the Vikings, who have given up 27 quarterback hits in five games and rank last in the NFL in yards per run.

“The offensive line is still a work in progress,” he said. “We’ll have to get better there.”

Since 2007, the Vikings have taken only two linemen in the first three rounds of a draft, and they have not been as successful in recent years at developing late-round linemen.

The Vikings selected guard Willie Beavers, who played tackle in college, in the fourth round of the 2016 draft. But he proved to be a disappointment and was the highest pick from this year’s draft not to make a 53-man roster out of training camp. After a stint on the practice squad, Beavers is now on the active roster. But he’s not an option at tackle.

Clemmings, a fourth-round pick in 2015, was expected to be the backup swing tackle in 2016 after a rocky rookie season at right tackle filling in for the injured Loadholt. But Kalil’s injury forced the Vikings to start Clemmings at left tackle. He struggled in pass protection against the Giants and then the Texans. On Sunday, Houston standout pass rusher Whitney Mercilus blew by Clemmings on a pair of sacks.

“There were a lot of times during the game he played well,” Zimmer said after watching tape from the Texans game. “Then he’ll have five just crazy things he does — he sets too wide, he lunges with his hands, he gets beat quickly. So we’ll have to get that fixed.”

Sirles, originally a backup to a backup, has held his own replacing Smith at right tackle.

Despite the slew of injuries along the offensive line, the Vikings are 5-0 entering their bye week, and after Sunday’s games they ranked 13th in the NFL in scoring. The line, though, could ultimately become a roadblock as they look to keep on trucking toward a Super Bowl.

“We’re just trying to win one game at a time,” Zimmer said. “I’m not going to worry about sustaining [success] for a long time. Each week, we’re just trying to win one game, figure out how to beat this team we’re playing and find a way with the guys we have.”