Samaras signed a new deal in March despite netting just three SPL goals last season, two of them against Rangers at Ibrox.
The Greece striker has failed to score this term for Celtic and has been the subject of criticism from supporters, but Lennon continues to pick him for big occasions.
Lennon backed Samaras at Friday's club's annual general meeting, but confessed he had to get more out of the 26-year-old - or pay the price.
When asked by a shareholder if he regretted handing Samaras a three-year contract, Lennon said: "No, I don't. The alternative was to let him leave for nothing.
"There was a lot of interest in him from other clubs. But he wanted to stay here and prove himself. So he is our player. I have to encourage him and eke the talent out of him because he has attributes.
"He is a player who could ultimately get me the sack. I am as much to blame as him for his performances but I can't give up on him."