Despite the heavy outlay on new playing staff in the summer by former boss Paolo Di Canio, Poyet now has his own targets.
New loan signing Alonso will bring real competition for places in Sunderland's defence after he agreed to join for the rest of the season from Fiorentina and the boss is delighted with his arrival.
"It is good to have competition and this will help us," Poyet told the Gazette. "I can confirm Marcos will be with us for the rest of the season on loan,which is something very important for us.
"I was always looking for a player at left-back or on the left side so I'm delighted he's here.
"It's competition for Andrea who is the only recognised left-back we have here.
"But it is important to say they are different sorts of players - Marcos and Andrea - so it helps us with our options."