Sunderland sign Darron Gibson and Bryan Oviedo from Everton

Sunderland have completed the signings of Darron Gibson and Bryan Oviedo from Everton for undisclosed fees.

David Moyes brings in the duo from his former club as he looks to bolster his relegation-battling squad.

Former Manchester United midfielder Gibson, 29, joins on an 18-month contract, while Costa Rica left-back Oviedo has signed until 2020.

"We've got Darron on an 18-month contract and I think he's a very good footballer," Moyes told Sunderland's official website. "He'll add a bit of quality with his passing and his play and I'd love him to add goals.

"He has a really good strike and if he can add goals from midfield it would be a big bonus."

Oviedo arrives following Patrick van Aanholt's move to Crystal Palace, and Moyes said: "Bryan is a very good player and he'll help us get forward. He's quick and overall he's a decent left-back.

"I signed him for Everton from Copenhagen as cover for Leighton Baines at the time, and he's only not getting in because of how well Leighton's done."

He added: "He's 26 which is a good age for us and I think he's a really good character -- a good boy -- and I'm hoping he's someone who will help us over the years."

The cash raised by Patrick Van Aanholt's departure to Crystal Palace allowed Moyes to return to his former club and snap up direct replacement Oviedo and experienced, but injury-plagued, midfielder Gibson.

Oviedo, 26, made just 68 senior appearances during his four and a half years on Merseyside, while 29-year-old Gibson managed one more in his five years.

Moyes, whose side faces high-flying Tottenham in the Premier League on Tuesday evening, said: `"Every player who is coming into Sunderland is a bit of a gamble. I don't think we could get an absolute nailed-on player, I don't think that's the case."

Everton boss Ronald Koeman said allowed the duo to move on so they could play first-team football.

"It's a good opportunity for them to play," Koeman said. "I'm happy for the boys. For Darron there was a lot of competition in midfield.

"In the situation of Bryan Oviedo, it was difficult. He was the back-up for Leighton in the left-back position but finally I changed my mind, I spoke to the player and he was always the perfect professional. I understand his feelings. It was difficult for him. He's got a new challenge to play in Sunderland.

"First of all [on him leaving] I said to him, 'No way, no chance,' because we need back-up and we need competition. But, as a football man, I changed my mind. I like the boy, he was working hard and that was the reason that he got the chance to go and play.

"It was difficult but I think if we get any problems in that position we have some good young ones and I think we can cope with the players we have in our squad."