The 25-year-old Belgium international is on the verge of moving to the Reds in an £8 million deal after an impressive campaign at the Stadium of Light last term.
Rodgers explained that he held talks with Reina before the end of last season to make him aware of his plans to sign Mignolet but insists that the Spaniard remains an "outstanding goalkeeper".
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"Pepe Reina and I went out for a meal a couple of months before the end of the season and I told him exactly what we were going to do, which was to provide real competition in that area.
"He was fully aware of my intention over the course of the last few months. It certainly wouldn't be a surprise to Pepe.
"Pepe is a fantastic goalkeeper but Simon Mignolet is a player that has done really well. He's also part of an emerging Belgium squad that has come into a golden era. He's very much a part of that.
"When you work with Pepe, he's a great man. A very committed man to the club and he's an outstanding goalkeeper."
Reina, who is currently with Spain's squad at the Confederations Cup, is adamant that he wants to remain at Liverpool despite the likely arrival of Mignolet.
"It doesn't change a bit," the 30-year-old told reporters. "I said it many times, I'm very comfortable and happy with Liverpool. Every team needs competition and when it's positive, it's very welcome. I'm going to welcome him, anything he needs I'm here."