Julio Arca says Sunderland will have to make decisions on David Moyes and their players quickly as they look to build a squad that can climb out of the Sky Bet Championship.
Sunderland's relegation from the Premier League was confirmed on Saturday when a 1-0 home defeat against Bournemouth - their 23rd loss of the season - put 17th place and safety out of reach.
Arca suffered relegation with Sunderland at the end of the 2005/6 season before moving on to Middlesbrough, where he spent a further six seasons before retiring in 2013 after a long battle with injury.
Now both of those sides face being relegated from the top division, with Boro possibly needing to win their final three games to avoid joining Sunderland in the second tier.
"The club needs to change a few things around but David Moyes is a good manager, he has got a lot of experience," said Arca, who now plays for Northern League side South Shields and could feature in the FA Vase final at Wembley later this month.
"They are going to have to start from scratch again and see what happens. This season didn't go the way he wanted and the club will think about it for the next few weeks and hopefully make a decision.
"I've been in the Championship as well and it is a hard division which is getting harder every season. There is more money in the Championship and teams are getting stronger.
"It's not going to be easy and I am sure Sunderland will have to spend money to get back in the Premier League like Newcastle did. It's about what you are going to do this summer. I am sure there is going to be a few changes and we'll find out during the summer.
"Relegation is the lowest you can feel in your professional career so I am sure they will all be disappointed what happened this season. It's all about thinking about next season, bouncing back and hopefully getting back in the Premier League as soon as possible.
"It was a big change in the club, thinking about what Sam Allardyce did last season. He got some good players in January and when Moyes came in he didn't have time to buy, and I think the club paid the consequences.
"I'm sure Moyes wanted to bring in more players, or more quality players, but the [current] players didn't do enough to keep Sunderland in the Premier League."