The 49ers won’t have Mike Evans this Sunday as they attempt to improve to 7-0 against the Falcons in Atlanta. But at least some help is on the way for their beleaguered receiving corps.

Coach Kyle Shanahan announced Friday that their leading receiver had been ruled out after sitting out practice for the second straight week. He attempted to play Monday night but aggravated the tendinitis in his Achilles and was forced to leave before halftime.

Despite dealing with broken ribs on top of his Achilles issue, Evans has been Brock Purdy’s go-to target, particularly around the sticks, with 25 first-down catches through six weeks.

Purdy, the NFL’s top-rated passer this season, will have to make do with tight end George Kittle, multifaceted running back Christian McCaffrey and a makeshift group of receivers missing Evans, Deebo Samuel, Demarcus Robinson, De’Zhaun Stribling and Ricky Pearsall.

The totality of the 49ers injury situation could leave them with fewer than 48 active players. Two typically healthy scratches, third-string quarterback Kurtis Rourke and backup offensive tackle Enrique Cruz, are expected to be suited up and ready to go in Atlanta.

“Those are two guys that’ll be our two emergency receivers in the game,” Shanahan joked. “I don’t think [I’ve] ever [played with fewer than 48] in my career. It’s a unique situation.”

While nobody can replace Evans’ production, with 420 receiving yards, three touchdowns and a 130.3 rating when targeted by Purdy, Christian Kirk could help lessen the blow.

Kirk, 29, is expected to make his 49ers debut in Atlanta. The free-agent signee injured his calf on the first day of training camp but returned to practice for the first time last week.

Kirk was a full participant in all three of the 49ers’ practices this week. Although he is officially listed as questionable, Shanahan confirmed that was merely procedural.

In anticipation of Kirk’s activation, the 49ers opened a roster spot by releasing defensive lineman Ogbo Okoronkwo, who they were expected to re-sign to the practice squad and elevate on Sunday.

Still, until Kirk is officially activated, Brandin Cooks is the lone healthy wideout on the active roster with more than 10 career receptions. Second-year, fourth-round pick Jordan Watkins and third-year, fourth-rounder Jacob Cowing will need to step up for an undermanned and inexperienced group.

The 49ers are shorthanded enough that it was a topic of discussion at practice this week, Shanahan said. He had to touch base with players who may be asked to fill in at different spots.

“Hope it doesn’t get to it, and odds are it won’t, but it definitely could,” he said. “There are always positions where you’re a few injuries away from those situations and now it comes down to a couple, so the percentages go up.”