Boyd, who he re-joined his first club on a short-term deal last weekend, began his career at Rugby Park in 2000, making more than 150 appearances before moving to Rangers in January 2006.
His career has since taken in spells at Middlesbrough, Nottingham Forest, Eskisehirspor and Portland Timbers.
The 29-year-old, who is the SPL's all-time top goalscorer with 164 goals, is in line to make his second Killie debut against Hibernian on Wednesday.
The experienced frontman thinks he is a better player than when he left seven years ago but accepts that is not enough to secure a first-team spot.
"I've improved as a player," he told Sky Sports. "You get to know the game and you learn things.
"I feel as if I'm a far better player than when I left but that's still not going to guarantee me a place in the team.
"I need to get my head down in training and there's a few games coming up that hopefully I can be involved in.
"Once I'm in hopefully I can stay in but there are a lot of quality strikers here who have been doing well and I know I need to work hard to get myself in the team."