New Orleans Saints left tackle Terron Armstead will undergo surgery Monday to repair a torn labrum in his shoulder, a league source confirmed to The Advocate on Friday.

Armstead is expected to miss four to six months after undergoing the procedure.

For a player who was set on putting two injury-filled seasons behind him, the new injury is a difficult setback. 

"Heartbroken when I found out I need surgery!" Armstead wrote on his Twitter account Friday. "No one is more frustrated than me after working so hard. I'll be back #WhoDatNation STRONGER!!"

The NFL Network reported the news first.

Armstead left the field during Wednesday's minicamp practice and did not return to the field on either Wednesday or Thursday. 

Saints coach Sean Payton declined to comment on Armstead's injury after practice on Thursday, citing his policy to not discuss injuries until required during the regular season.

Armstead, who is regarded as one of the NFL's best left tackles when healthy and signed a five-year, $66.671 million extension during the summer of 2016, has been plagued by injury the past three seasons.

A knee injury in 2015 cost him three games and forced him to play through extreme pain once he returned, and lingering problems with the left knee and quadricep limited him to just seven games last year before going on injured reserve.

Armstead, whose repetitions had been limited somewhat in this summer's practices, had been hopeful that he'd put the knee problems behind him this offseason, targeting a return to 100 percent before the start of training camp at the end of July. 

"I just want to be out there for my team," Armstead said. "Take it one game at a time."

Then the shoulder injury struck with only a few hours left in the Saints' summer workouts, adding Armstead to a list of high-profile injuries New Orleans is dealing with this summer. 

Elsewhere on the offensive line, center Max Unger underwent surgery in May to repair a space between the bones in the Lisfranc area of his foot, an injury that is expected to keep Unger out of action until late in the preseason.

"Surgery this time of year is obviously not what you want, but this is an injury that just kind of developed," Unger said earlier this week. "The No. 1 thing is we got it fixed, and hopefully I'll be able to come back Week 1."

New Orleans is also awaiting a decision from defensive tackle Nick Fairley, who has undergone three evaluations by specialists after team doctors detected a change in the condition of his heart. Fairley was diagnosed with an enlarged heart before the Detroit Lions drafted him in the first round in 2011, but the change is significant enough that one specialist recommended Fairley retire from football.

Armstead's injury represents another high-profile blow to the talent base the Saints have assembled, and a frustrating setback for a player whose injuries have kept him off the field the past two years.

"I hate it," Armstead said.

With Armstead out, the Saints may turn to rookie Ryan Ramczyk, the rookie tackle New Orleans selected with the final pick of the first round of April's draft.

Ramczyk, who recovered from January surgery to repair a torn hip labrum in time to participate in this week's mandatory minicamp, was expected to play on the right side primarily, but he took a few snaps on the left side during Thursday's practice.

"I'm excited to have a guy like Ryan that's asking questions, that's interested in how to get better, that's taking coaching. He's doing all the things you want," right tackle Zach Strief said. "I think he's going to be a really good player."

Ramczyk's presence means the Saints may not have to do as much shuffling to fill in for Armstead on the left side. When Armstead was injured last season, Andrus Peat kicked out from left guard to play the outside, but Peat hasn't been asked to play any tackle so far this summer.

"Getting a full season at that one spot, I think that'll be beneficial," Peat said. "This whole OTAs and minicamp, I've been at left guard, so I've already felt like I've improved at guard."

Peat was also looking forward to a full season teaming with Armstead, a player who is a devastating talent when healthy.

Unfortunately, the wait will be a little longer to find out how good the two can be together.

Follow Joel A. Erickson on Twitter, @JoelAErickson.