What noun means opposite of "slacker" but is less extreme than "overachiever"?

Question

Sample sentence: "John was not a slacker. He was reliable and productive. Not quite an overachiever per se but rather a ____. What needed to be done, he always got done. No more and no less."

(Preferably one word noun to fill the blank).

Answer 1

How about workhorse?

Workhorse

NOUN

1. A horse used for work on a farm.

   1.1 A person or machine that dependably performs hard work over a long period of time.
   ‘the aircraft was the standard workhorse of Soviet medium-haul routes’

That would be my choice. There's also self-starter:

Self-Starter

NOUN

1. A person who is sufficiently motivated or ambitious to work on their own initiative without needing direction.
   ‘he was the self-starter who worked his way up from messenger boy to account executive’

Hope this helps!

Answer 2

A go-getter is someone who is productive, active, and energetic. From the OED:

An enterprising or ambitious person; a person who is determined or likely to succeed; an achiever.

"We want to appoint young, enthusiastic and ambitious go-getters who want to grab hold of this opportunity and make the most of it."

It's a common phrase in US English, though I'm not sure how common it is in other dialects.

Of course, one man's "overachiever" is another man's "go-getter"; there's an inherently subjective judgement in deciding how productive is "overly" productive.

Answer 3

Trouper also works as a sort of veteran of the good and bad times.

trouper

An experienced or dependable worker or associate

Collins English Dictionary, 12th Ed.

Answer 4

A rock

One that is similar to or suggestive of a mass of stone in stability, firmness, or dependability: The family has been his rock during this difficult time.