Already without their star running back and starting right guard, the Vikings will have to finish the season out without another key cog in their running game.

Right tackle Phil Loadholt, arguably the team’s best run-blocking offensive lineman, tore a pectoral in the fourth quarter of Sunday’s 24-21 loss to the Green Bay Packers and will miss the rest of the season, Vikings coach Mike Zimmer announced Monday.

Loadholt, who has not yet been placed on injured reserve, will undergo surgery Friday.

“I think Phil is a great person. He’s very conscientious, works hard. He’s got a great heart. So that’s just part of football,” Zimmer said. “Obviously we’ll miss him. But we’re not going to let it hold us back from what we’re trying to get done.”

Mike Harris replaced Loadholt during the final Vikings possession, which resulted in a touchdown. He has appeared in seven games this season as a reserve, seeing snaps at both right guard and right tackle after in-game injuries to starters.

Zimmer said Harris will “probably” be the team’s right tackle this weekend when the Vikings play host to Carolina. But undrafted rookie Austin Wentworth might also be considered for the position, and Zimmer didn’t rule out the Vikings adding another tackle to the roster.

Harris is hopeful he will get the call, which he said would be a “great opportunity” to build on what he has accomplished in his young career. The 25-year-old started 12 total games in 2012 and 2013 for San Diego. The Vikings claimed him in late August when the Chargers waived him following the preseason.

“It’s been awhile since I’ve [started] but I’m just going to take [the opportunity] and go play hard,” Harris said. “I know my team is counting on me to perform so that’s just what I’m going to take it as and just enjoy it for what it is. It’s unfortunate for Phil because he’s out, but I have to go in there and not miss a beat because he’s a great tackle.”

Loadholt is in his sixth NFL season, a season that has been a disappointment considering he is the NFL’s third-highest-paid right tackle. He has struggled in pass protection, allowing five sacks and 33 total pressures, according to Pro Football Focus. Only seven NFL tackles, including teammate Matt Kalil, have surrendered more pressure.

But once again, running backs have had success running behind the 6-8, 343-pound Loadholt. When running off right tackle, the Vikings have rushed for 369 yards on 74 carries — an average just shy of 5.0 yards per pop — with four touchdowns. Their longest run, wide receiver Cordarrelle Patterson’s 67-yard touchdown in the season opener, came around the right end.

“Big Phil, man. It hurts. It hurts to see your teammate go down like that,” cornerback Captain Munnerlyn said. “But at the same time, somebody’s got to step up and make some plays.”

The loss of Loadholt was the latest blow to the Vikings running game, which is averaging 4.6 yards per carry but has produced inconsistent results overall, especially the past two weeks.

The Vikings have been playing without starting running back Adrian Peterson since Week 2 and will be without him for the rest of the season as he serves his NFL suspension. They also lost starting right guard Brandon Fusco in Week 3, coincidentally to a torn pectoral as well.

“Everybody has injuries,” Zimmer said. “That’s just the way it goes. That’s how things happen. You just got to keep playing.”

Up next for the Vikings are the Panthers, who rank tied for 23rd in the NFL in rushing yards allowed per carry at 4.4. Only Atlanta has given up more rushing touchdowns.

After Sunday, though, that patchwork right side of the offensive line will face much tougher tests against the New York Jets, Detroit Lions and Miami Dolphins, who all rank in the top 11 in rushing defense.