Cook linguine in a large pot according to package directions (minus a couple minutes of cook time for the pasta to be al dente).

Reserve 1/2 cup of pasta water and set aside. Drain the pasta in a colander and set aside.

In a large sauté pan over medium-high heat, add the olive oil. Add chicken, salt and pepper and sauté until cooked.

Add a little pasta water and Swiss chard to the pan with the chicken. Toss until Swiss chard is wilted, about 1 minute.

Return linguine to the sauté pan. Add the feta and lemon juice. Toss the mixture until the feta cheese begins to melt, then season with salt, pepper and red pepper flakes.

Serve warm.