SEATTLE -- The usual dizzying offseason whirl of trades and signings have been replaced with a more pedestrian approach by the Seattle Mariners this year.

General manager Jerry Dipoto said Tuesday that's by design and an indication of where he believes the Mariners are with their roster entering the next stage of their rebuilding plan.

"We don't feel like we've been quiet, or slow," Dipoto said. "If that's what it seems to you all, I apologize. I know it's not our normal rate of activity, but that is more where we are in our build, truly. We've added quite a bit to our team already."

That's not to say Dipoto won't be busy over the next month before the Mariners report for spring training in Arizona. While the primary focus going into the 2021 season is going to be the continued development of Seattle's young stars -- highlighted by AL Rookie of the Year Kyle Lewis -- and the eventual arrival of some top prospects, Dipoto still has needs to fill before the start of the season.

Primarily, Dipoto would like to see another arm or two added to the bullpen, another possible starting pitcher brought into the mix and a left-handed bat for the lineup, either at second base or as a utility player who could be part of the outfield rotation.

"It has been a slow-to-develop offseason market, particularly at the top of free agency, but that hasn't really been a focus for us," Dipoto said. "I think you have seen over the course of particularly this last four or five weeks that the market is moving, and you're starting to see a lot of players that you recognize, recognizable names coming off the board."

The primary focus of Seattle's offseason thus far has been on improving a bullpen that was among the worst in baseball a season ago.

So far, that's meant the additions of Rafael Montero via trade from Texas and the signing of Keynan Middleton as a free agent. Seattle also signed right-handed starter Chris Flexen to a two-year deal.

The lack of moves is partly because the Mariners will go into spring training and the start of the season still trying to learn about some of their own players. Can Lewis replicate his Rookie of the Year performance over a full season? Can J.P. Crawford play Gold Glove shortstop for a full season? What about young starting pitchers Justus Sheffield and Justin Dunn?

The truncated 2020 season gave Seattle a taste of what some of its young prospects might bring. But until they can prove it over a longer stretch, Dipoto plans to remain cautious about making any splashy moves.

That said, if the Mariners find themselves sniffing around a playoff spot come midsummer, Dipoto's approach might change.

"If things break well for us and we get into midsummer, and we stay close to this thing and we do have an opportunity to sneak up on the back of the playoff field, that's a possibility for us and would be a goal," Dipoto said. "Young teams tend to jell quicker than you might think. We can't go in expecting that we're going to run to the top of the American League West. But I think we can set the goal of competing for a playoff spot and we'll see how it goes."