"They made my life easier. I'm exhausted of training".
The 29-year-old played a key role as Chelsea won the Premier League title in Conte's first season at the club but was subsequently told he was surplus to requirements by the Italian.
The Spain global re-joined Atleti from Chelsea in September, but the move could not be officially ratified as it was negotiated outside the transfer window and Los Rojiblancos were serving a transfer ban.
"Seriously, the supporters, the people at the club and my teammates helped me a lot. It's a great club and there are only good memories".
Lions beat Packers 35-11 to finish up season at 9-7
Brett Hundley was 14-of-24 passing for 172 yards with a touchdown and two interceptions for a passer rating of 59.7. The Detroit Lions will close their 2017 schedule with a final game at Ford Field against the Green Bay Packers .
"It's true that there are players of great quality and at the end of the day it is the coach who will decide".
Atletico plays Lleida Esportiu in the King's Cup on Wednesday.
"It's a challenge", he said.
Costa was officially presented at the Wanda Metropolitano stadium on Sunday, alongside fellow Spain team-mate Vitolo, who signed from Sevilla in July. Atletico signed him in the summer and loaned him to Las Palmas for the first half of the season, but he is now free to make his debut for Atleti.