I'm not familiar with Picard's 20 year command of the Stargazer (where does that come from?).
I know that he took over once when the Captain of the Stargazer was killed. And that it was damaged by Cardassians when he was ordered to approach them with a truce and had to retreat. And 9 years prior to "The Battle" it was abandoned after destroying a Ferengi ship. If he was back near Cardassian space it would sound like he would have opportunities to get the ship refit and upgraded.