By Marcus ChhanFollow @@MarcusChhan
The 28-year-old ASEAN Basketball League (ABL) veteran was put on the Slingers' injured reserve list earlier in the month after he was no longer able to play through the persistent and painful foot injury.
"I am disappointed," Jeffers told FOX Sports.
"It's sad because I've been a part of the team for so long. I've been able to fight through almost anything. Just not being able to overcome what seems like a little injury, not to be able to push through it, it's a bit disappointing.
"I've been playing with it [Plantar Fasciitis] through the whole season. I have not been able to go 100% because of the injury and that's one reason why I needed to back off because if I can't push myself then I can't push my team-mates - and if I can't push my team-mates then I can't be the leader I normally am."
Jeffers, who has been with the Singapore outfit for four seasons, is not expected to return to the Slingers line-up in the current campaign although the Californian is still hoping to play some part in what he thinks might be his last spell as a professional basketballer.
"Right now, it's up in the air," he said.
"With how the team is going about it, they are not expecting me to come back for the whole season. For me, I would like to come back [this season] but at the same time, I am trying to push through it [the injury] and so there's really no point in coming back if I am not 100%.
"Some days it [the injury] has its good days and bad days. But overall, I just want to be able to do normal activities without pain is what it comes down to now."
Jeffers added: "To give you a definite answer, I would say after the 2013 season, I would not consider coming back at a professional level."
Jeffers started all of the Slingers' first eight games of the new ABL season averaging 17.5 points and 11.9 rebounds per contest.
He remains contracted with the Singaporeans until the end of the season and will continue to help the club with its strong community drive.
American centre Donald Rashaad Singleton has been drafted in by the Slingers to fill the void left by the injury to Jeffers.