The Biancocelesti boss hailed the Spanish striker's movement during Saturday night's 1-1 draw with the Italian champions at the Stadio Olimpico.
The Spain international earned the Bianconeri a 1-1 draw on Saturday with a looping header, after Lazio had moved into the lead through an Antonio Candreva penalty following Gianluigi Buffon's foul on Miroslav Klose and subsequent dismissal.
Reja acknowledged how formidable the visitors still looked even when down to 10 men, praising his team's spirit for battling the Turin giant to a stalemate.
"The trouble is with Llorente it doesn’t matter how you mark him, he’s going to get the header, so you need to double up and protect the knockdown," the 68-year-old told reporters after the game at the Stadio Olimpico. "Juventus bypassed our midfield and started to send balls in for Llorente that were very dangerous. They are very talented and at a very high level, so it was not easy even against 10.
"We reacted very well. Klose had two or three good chances and I had hoped we would win. We were a little unlucky to hit the woodwork twice.
"Perhaps we should’ve done better on the counterattack. But Marco Storari also performed some extraordinary saves.”
Reja, who led the capital outfit between 2010 and 2012, returned to his post following the departure of Vladimir Petkovic in January. The Coppa Italia holder currently sits ninth in Serie A.