Two Acting Ministers sing praises about Dr Koh Poh Koon, so why is he not good enough for GE 2011?

Questions: If Dr Koh Poh Koon is such a good catch for the PAP, then why wasn't he fielded in GE 2011? Is it because he doesn't even measure up to candidates like Tin Pei Ling? Are Punggol East residents getting a fourth-tier candidate from the PAP for the by-election?

XIN MSN News, 14 Jan 2013
Acting Ministers Tan Chuan—Jin and Chan Chun Sing spoke on Sunday in support of Dr Koh Poh Koon — the People’s Action Party’s man for the Punggol East by—election.
Both said they have known Dr Koh for many years and described him as a sincere man who is passionate about making a difference.
Acting Minister for Manpower Tan Chuan Jin said: "Poh Koon is a very good man. He’s very sincere very passionate, I think in all the things that he does. So whether as a doctor, and certainly now in his possible capacity as a Member of Parliament, possibly beyond that depending on what plans there are — Poh Koon is someone I trust, someone who I know has the people’s needs at heart, and he’s someone who cares a lot for society as well."
Mr Chan, who is Acting Minister Social and Family Development, said: "He has just embarked on a new career in the private practice and the fact that he is prepared to set that aside to come forward and serve the people of Singapore — I think that speaks a lot about this character. Full story