Coach Ken Niumatalolo is continuing to work on Navy’s rotation at several positions ahead of the Sept. 1 opener vs. Notre Dame in Dublin. (Ricky Carioti/WASHINGTON POST)

The Navy football team will board a plane to Ireland on Tuesday Wednesday for its Sept. 1 opener against Notre Dame in Dublin, and until then Coach Ken Niumatalolo and his staff are continuing to sort out the team’s rotation at several positions, most notably on defense.

Outside linebacker is of particular concern in the wake of a recent injury to Chris Johnson. The sophomore had been making a strong case in training camp to be a starter, but a knee injury during Friday’s scrimmage has left his status in doubt for the immediate future and perhaps long term.

Johnson was to have a second opinion on his left knee, but Niumatalolo and defensive coordinator Buddy Green are girding for the worst in case there’s confirmation of a torn anterior cruciate ligament.

“We were real disappointed when we lost Chris,” Green said. “Chris Johnson was having one of the best camps of anybody we’ve had around here in a long time. Really good speed. When we lost him, we felt for him and for our team.”

The Midshipmen did receive some reinforcement at the position with Josh Tate back in the fold. The sophomore missed training camp after failing the physical readiness test required to clear players to practice.

Tate recently passed the test, and he was on the practice field Wednesday afternoon working with the second team. Green lined up Tate at striker, which is the right outside linebacker spot that Johnson had been occupying, and is ascending quickly on the depth chart.

“These guys have got to earn their spots in working back,” Niumatalolo said of Tate as well as wide receiver Brandon Turner and cornerback Aubrey Felder, who also recently passed the conditioning test.

Obi Uzoma also has caught the attention of the defensive coaching staff, which has used him at striker in packages with starting raider Keegan Wetzel. Uzoma played extensively during Saturday’s scrimmage at Navy-Marine Corps Memorial Stadium and figures to do so again when the Midshipmen scrimmage for the final time on Friday afternoon.

Wetzel, meantime, is a senior who last season started one game at left outside linebacker and played in 11 overall. Jordan Drake also lined up at raider, although he is listed No. 2 on the depth chart at striker.

“For Navy football, especially defense, it’s being tenacious and run to the ball,” said senior inside linebacker Brye French, who started nine games at striker last season. “I mean, that’s got to be ingrained in everyone’s minds. Yeah, learn the defense and stuff like that, but the biggest thing is getting guys to run to the ball. For the young guys, it takes some time.”

Midshipmen note: Niumatalolo said he has decided freshman Nick Sloan will be the starting place kicker and classmate Austin Grebe the backup. Both made 20-yard kicks at the end of practice on Thursday while David Reisner, another freshman, missed two of three tries.

Sloan and Grebe will be with the Midshipmen on their trip to Dublin, as will sophomore Colin Amerau, who is the kickoff specialist.

“Now with the ball on the 35, that’s a huge advantage,” Niumatalolo said of a rule change regarding where kickoffs are spotted. “Just being able to kick that into the end zone, letting someone start at the 25. That position has become a valuable spot.”