Luis Suarez is "blowing up LaLiga" to prove to Barcelona that he is not finished, according to Gustavo Poyet.
Barca made the decision to allow Suarez to leave in the close-season after a successful six-year stay at Camp Nou.
Domestic rivals Atletico Madrid moved swiftly to sign him on a two-year contract in September and have reaped the rewards.
Uruguay international Suarez has scored 12 goals in 15 league games, adding two assists, and his side sat seven points clear at the top of the table heading into the weekend's top-flight action.
His compatriot Poyet, who formerly starred with Real Zaragoza, Chelsea and Tottenham, believes Suarez has been desperate to show he is not past his best, having turned 34 this month.
Discussing why he thinks Atletico are title favourites, Poyet told Stats Perform News: "They took a very important decision which would not be easy for some people.
"It was easy for El Cholo [head coach Diego Simeone], from what I know of him.
"Bringing in Luis Suarez as Barcelona didn't want him, bring him in now. And Luis went with his mentality, 'I will show you who I am'.
"A bit like a Uruguayan I am, 'You don't want me? Am I over? Let’s see!'.
"And this is blowing up La Liga."
Leaving Barcelona gave Suarez the push he needed to make changes and give something extra, in the view of Poyet.
He added: "What it shows is that sometimes football players need something different, just something.
"It can be a different treatment or being tougher [on them]. But they need something to react to.
"He was low, not bad, but like the [Barcelona] team, he was low. He needed a new challenge and sometimes it is tough to get it in the same club.
"It can happen with arrival of a new manager, or signing a new player who becomes a rival of yours. There are different ways, but if it does not happen, it looks difficult.
"However, there is no doubt that joining such a special team like Atletico with such a special coach, similar character [to Suarez], you get it and he is showing that extra [effort] needed.
"Sometimes we all need to realise. Get out from the club and notice that you have to do something to change the situation.
"I was not doubtful on his performance, especially playing in that system and having that responsibility.
"I don't forget it that it was him or Diego Costa [playing] at the beginning, sometimes both together. But at the time, Costa had gone, with all the respect to other players, it was only Luis Suarez.
"That also gives him the responsibility on scoring 20 to 30 goals and Luis accepts it in a natural way."
Atletico play away to Cadiz on Sunday and Poyet was asked if he thinks they can finish the job and win the title in the second half of the season.
"I do, for two reasons," he replied. "First, they are very strong, all credit to them, and also, because Real Madrid and Barcelona are currently really poor.
"I don't see any consistency in any of them. Unfortunately, when I look at Barcelona or Real Madrid I don't know what to expect from them, I don't know what is going to happen.
"And that proves it is a year for other teams like Atletico Madrid of El Cholo to go the distance, to actually show they belong at the top without any falling.
"We will see how they can keep it up. We know everything can change with injuries, sending-offs, everything can become really difficult. But no doubts, the main candidate is Atletico Madrid."