Moritz Leitner left Lazio to return to the Bundesliga with Augsburg on Tuesday.
The midfielder made only two appearances with Lazio after signing in the summer from Borussia Dortmund.
He previously played on loan at Augsburg in 2011 and helped the the club win promotion to the top flight.
"My first spell at FCA, which was crowned with promotion to the Bundesliga, was terrific," the 24-year-old told the club's website. "I only have positive memories of it so it quickly became clear to me that I wanted to take this opportunity to return to the Bundesliga.
"I'd like to thank everyone involved for their confidence and I look forward to getting to know the team and being able to wear the FCA shirt for a long time."
Lazio also parted ways with left-back Vinicius Freitas, who joined AEK Athens, while 20-year-old Joseph Minala went on loan to Serie B club Salernitana.