Complex sentence: The Pittsburgh Penguins signed Sanderson as a free agent in 1977-78; he played 13 games with the Penguins and eight games in the minors before retiring.
Split into simpler sentences: The Pittsburgh Penguins would sign Sanderson as a free agent in 1977-78. Sanderson would play 13 games with the Penguins and eight games in the minors before retiring.