The trade market for starting pitchers could be stocked with aces this summer, and the Padres are expected to be one of the clubs in the mix.

Bolstered by the surprising free-agent addition of Manny Machado and the strong starts of rookie sensations Fernando Tatis Jr. and Chris Paddack, San Diego is firmly in contention in the National League. But the club still has a significant need in the rotation and will likely seek outside help before the Trade Deadline.

Free agent Dallas Keuchel doesn't appear to be one of their options, however, as MLB Network insider Ken Rosenthal reports in an article for The Athletic that the Padres “prefer a trade for a top-of-the-rotation starter such as the Indians’ Trevor Bauer.”

Rosenthal wrote earlier this month that San Diego doesn’t see Keuchel as a fit because he is too similar to many of its other soft-tossing starters, such as Eric Lauer, Joey Lucchesi, Nick Margevicius and Matt Strahm.

Facing financial restrictions, Cleveland shopped Bauer, who can become a free agent after the 2020 campaign, and Corey Kluber, who is currently on the injured list with a fractured ulna bone in his right forearm, in the offseason. The Indians could revisit trade discussions this summer if their deficit in the American League Central continues to grow, and the Padres certainly have the prospects to entice them.

But Bauer isn’t the only starter the Padres might pursue. Here are some others who could be available for the right package of prospects.

Max Scherzer, Nationals

Scherzer remains as dominant as ever -- his 2.33 FIP leads all qualified starters and is a career best -- but the Nationals are in the midst of another disappointing campaign, and the ace right-hander is now 34 years old. Moreover, he is still owed $105 million in deferred money that will be paid out over 2022-28, according to Cot’s Baseball Contracts, and he will gain a full no-trade clause via 10-and-5 rights after this season. As difficult as it would be to part with Scherzer, this might be the best time for Washington to trade him.

Noah Syndergaard, Mets

Syndergaard’s 4.93 ERA isn’t reflective of an ace performance, but the right-hander still possesses a terrific arsenal and has posted a much-more-palatable 3.67 FIP. The Padres reportedly had interest in trading for Syndergaard last summer and during the offseason, and MLB.com’s Anthony Castrovince recently listed Syndergaard to San Diego as one of five not-so-crazy trade ideas. Although Syndergaard still has two years of team control remaining after this one, he is likely going to want an extension close to the five-year, $137.5 million deal Jacob deGrom signed in March, especially considering he is more than four years younger than his teammate. If the struggling Mets tire of his inconsistency and don’t want to pony up that kind of dough for another starter, they could shop him.

Madison Bumgarner, Giants

The Bumgarner era in San Francisco is likely nearing its end, it’s just a matter of where he ends up. The impending free agent may not be a top-tier ace anymore, but he remains effective, and his postseason dominance is sure to be of interest to many contenders. Bumgarner has encouragingly increased his velocity this season after experiencing a decline in recent years, and his K-BB% is up from 12 percent in 2018 to 20.3 percent. Needing an influx of young talent, the Giants aren’t likely to have many qualms about dealing Bumgarner to a division foe.

Marcus Stroman, Blue Jays

After dealing with injuries and posting a 5.54 ERA in 2018, Stroman has bounced back in a big way this year, notching a 2.81 ERA over 11 starts. However, the Blue Jays are at least a year away from contending, and Stroman can become a free agent after 2020. Although Stroman has more in common with Keuchel than he does with the first three pitchers on this list, relying on a heavy dose of grounders to succeed, the Padres discussed a trade for the 28-year-old in the offseason and could still be interested given his renaissance.

Mike Minor, Rangers

While the additions of Lance Lynn, Shelby Miller, Drew Smyly and Edinson Volquez haven’t worked out all that well for the Rangers, Minor has carried the rotation on his back and is one of the reasons why the team is above .500. Over 10 starts, Minor has recorded a 2.64 ERA with 67 strikeouts in 64 2/3 innings. That said, he’s 31 years old, has a history of shoulder problems and can become a free agent in a year, so his trade value might never be higher for Texas.

Matthew Boyd, Tigers

Boyd is one of this year’s most surprising breakout players, recording a 3.11 ERA with a personal-best strikeout (29.6 percent) and walk (5.2 percent) rates. That’s a stark contrast to what he did from 2015-18, a span in which he had a 5.07 ERA with a 19.9 percent strikeout rate and a 7.7 percent walk rate. Boyd is still three-plus years away from free agency, so it will likely take a haul for the Tigers to part with him, but Detroit could shop him anyway because he’s already 28 years old, and because the team has so few trade assets on the Major League roster.