A modified high-cis polybutadiene polymer having polymer chains bonded to a residue of a functionalizing compound having formula (I) as follows where X is a group reactive with the living end polymer chains and is selected from the group consisting of cyano, epoxy, ketone, aldehyde, ester, and acid anhydrides, R 1 is selected from hydrocarbylene of C 1 -C 20 , preferably C 1 -C 10 , more preferably C 1 -C 3 , wherein each of the foregoing optionally contain one unsaturated carbon-carbon bond, each R' is selected from alkoxy of C 1 -C 20 , preferably alkoxy of C 1 -C 10 , more preferably alkoxy of C 1 -C 6 , most preferably alkoxy of C 1 or C 2 , and R" is selected from alkyl of C 1 -C 20 or aryl of C 6 -C 20 , preferably alkyl of C 1 -C 10 or aryl of C 6 -C 14 , more preferably alkyl of C 1 -C 6 or aryl of C 6 wherein each polymer chain is bonded to the residue of the functionalizing compound through the X group, and the modified high-cis polybutadiene polymer has a cis 1,4-bond content determined by FTIR of 92-98%, an initial Mooney viscosity ML 1+4 at 100 °C determined using the method of the description of 20-100, preferably 30-80, and an aged Mooney viscosity ML 1+4 at 100 °C of no more than 120, preferably no more than 105, wherein the aged Mooney viscosity is determined after aging at 100 °C for 2 days. polymer chains bonded to a residue of a functionalizing compound having formula (I) as follows where X is a group reactive with the living end polymer chains and is selected from the group consisting of cyano, epoxy, ketone, aldehyde, ester, and acid anhydrides, R 1 is selected from hydrocarbylene of C 1 -C 20 , preferably C 1 -C 10 , more preferably C 1 -C 3 , wherein each of the foregoing optionally contain one unsaturated carbon-carbon bond, each R' is selected from alkoxy of C 1 -C 20 , preferably alkoxy of C 1 -C 10 , more preferably alkoxy of C 1 -C 6 , most preferably alkoxy of C 1 or C 2 , and R" is selected from alkyl of C 1 -C 20 or aryl of C 6 -C 20 , preferably alkyl of C 1 -C 10 or aryl of C 6 -C 14 , more preferably alkyl of C 1 -C 6 or aryl of C 6 where X is a group reactive with the living end polymer chains and is selected from the group consisting of cyano, epoxy, ketone, aldehyde, ester, and acid anhydrides, R 1 is selected from hydrocarbylene of C 1 -C 20 , preferably C 1 -C 10 , more preferably C 1 -C 3 , wherein each of the foregoing optionally contain one unsaturated carbon-carbon bond, each R' is selected from alkoxy of C 1 -C 20 , preferably alkoxy of C 1 -C 10 , more preferably alkoxy of C 1 -C 6 , most preferably alkoxy of C 1 or C 2 , and R" is selected from alkyl of C 1 -C 20 or aryl of C 6 -C 20 , preferably alkyl of C 1 -C 10 or aryl of C 6 -C 14 , more preferably alkyl of C 1 -C 6 or aryl of C 6 wherein each polymer chain is bonded to the residue of the functionalizing compound through the X group, and the modified high-cis polybutadiene polymer has a cis 1,4-bond content determined by FTIR of 92-98%, an initial Mooney viscosity ML 1+4 at 100 °C determined using the method of the description of 20-100, preferably 30-80, and an aged Mooney viscosity ML 1+4 at 100 °C of no more than 120, preferably no more than 105, wherein the aged Mooney viscosity is determined after aging at 100 °C for 2 days. <EOS>