MIAMI -- From the start of the Hot Stove season, the Marlins have said they are open to exploring all avenues to improve their big league roster. Now, the free-agent pool has expanded after Monday’s tender deadline.

“That universe of available players changed by 56,” Marlins president of baseball operations Michael Hill said. “We’ve already met as a baseball operations group to go through the newly available players. We’ll continue to be thorough as we look for ways to improve our club.”

In all, 56 players were non-tendered on Monday, and they now join the free-agent market.

Also on Monday, the Marlins made their first significant offseason moves by claiming first baseman Jesús Aguilar off waivers from the Rays and acquiring infielder Jonathan Villar from the Orioles for lefty pitching prospect Easton Lucas, Miami’s 14th-round pick in the 2019 MLB Draft.

“[Monday] was just the first step in adding to this club and putting us in a better position to have a successful 2020 season,” Hill said.

The Marlins are expected to be active at the Winter Meetings, which begin Monday in San Diego.

Improving the offense is the highest priority, followed by adding bullpen depth.

In free agency, the Marlins are primarily looking to sign versatile outfielders on one- or two-year deals. The organization is deep on outfield prospects, so it doesn’t want to block them. According to MLB Pipeline, 11 of Miami’s Top 30 prospects are outfielders.

Yasiel Puig and Avisail Garcia are possible free-agent targets, with Nicholas Castellanos, one of the most coveted free agents, being a less likely possibility.

An interesting outfielder who will be explored is Steven Souza Jr., after he was non-tendered by the D-backs on Monday.

Souza missed all of 2019 due to left knee surgery. If healthy, Souza could be a low-risk, high-reward signing.

Miami also is in the market for a backup catcher, and free agent Francisco Cervelli is available.

Cervelli, who was with the Pirates last year, came up with the Yankees, where he was a teammate of Marlins chief executive officer Derek Jeter.

The additions of Aguilar and Villar address infield needs.

Villar, who played mostly shortstop and second base last year with the Orioles, is expected to see time at third base and in the outfield. That means Brian Anderson will also work at third base and right field. Garrett Cooper is an option in a corner outfield spot, as well as at first base.

“There are more players on the market for us to explore, and we’ll see how it all unfolds,” Hill said. “But the bottom line is we know we need to still improve."