With just one Trade Deadline this year, the rumor mill could churn faster than ever over the coming weeks. General managers are probably spending every waking moment wondering which moves could improve their teams.

But let’s not forget the other additions; the baked-in enhancements already residing on contenders’ rosters. The grind of a 162-game season means you don’t always get a star’s best contributions in April and May. Here’s a look at players whose returns -- from either injury or ineffectiveness -- could impact September and October just as much as the big Trade Deadline acquisition.

ALREADY BACK IN FORM

Mike Clevinger, Indians
Returned: June 17

Don’t sleep on just how dominant Clevinger was before he hurt his back in his second start of the year. Clevinger’s fastball was exploding out of his hand in those first two outings, sitting 94-96 mph and topping out at 97.6 mph -- big news for a pitcher who had never hit 97 until he altered his mechanics last September. He’s been even stronger since he came off the injured list, besting that 97.6 mph pitch 13 times across four starts and topping out at a career-best 99 mph on June 28 in Baltimore.

Clevinger was already a top-15 starter by FanGraphs WAR last year. With his new fireball, he’s one of MLB’s 10 best starters by expected wOBA (xwOBA), which looks at contact quality, walks and strikeouts. He might help the Indians’ front office reconsider their position at the Deadline, especially with the Tribe much closer to the Twins than a few weeks ago.

Joe Kelly, Dodgers
Turnaround point: June 2

Kelly wasn’t sidelined, but he certainly didn’t start the way the Dodgers envisioned when they signed him to a three-year, $25 million deal last December. The righty jogged to the Dodger Stadium mound on June 2 carrying an 8.35 ERA before he struck out two of the three Phillies he saw to close out an 8-0 L.A. win.

As it turns out, that seemingly irrelevant blowout appearance was the start of a major hot run: Kelly owns a 1.29 ERA in his last 13 appearances, with 22 strikeouts, seven walks and a .170 opponents’ average. Statcast says that’s not a fluke: His .195 xwOBA in that span is tied for fourth-lowest in baseball out of 345 qualified pitchers.

This isn’t the first time that Kelly has tantalized with his stuff and his performance in small samples. But this is the super-stuff reliever the Dodgers invested in, and while they’re still undoubtedly a buyer in the reliever market, he could make that search a little less urgent if he keeps this up.

JUST GOT BACK

Corey Seager, Dodgers
Returned: Friday

Seager got back in the Dodgers’ lineup to open the second half in Boston, and he’s a bonus addition to L.A.’s already powerful lineup. He hasn't gotten a hit yet since returning, but Seager was extremely hot before he strained his left hamstring, slashing .382/.447/.671 over the three weeks leading up to his injury. The NL’s scariest offense adds a hitter who owns a career 130 wRC+ and was a top-10 player as recently as 2017.

ON THE WAY

Carlos Correa, Astros
Expected return: Late July

Correa could start his Minor League rehab assignment next week for the fractured rib he suffered in May, though he won't be eligible to come back until at least July 26 after the Astros placed him on the 60-day injured list Friday. His return would boost an Astros offense that is already tops baseball in weighted runs created plus. Correa was clearly compromised by a back injury last year, but his hard-hit and barrel rates this year were back up toward his 2015-17 averages (as was his .907 OPS) before he landed on the IL. Houston will more likely be focused on securing home-field advantage in the postseason by the time Correa shakes off the rust, and his bat (not to mention his glove) could help them do just that.

Nathan Eovaldi, Red Sox
Expected return: July

Eovaldi had the same elbow procedure he underwent last year, when he came back healthy enough to be a postseason hero for the Red Sox. He’d be a hero again if he returns as a closer, as expected, and turns around Boston’s bullpen, which is tied for the AL lead with 18 blown saves (including eight in June). That unit appeared to run out of gas entering the break, so perhaps Eovaldi and his high-octane fastball -- which glimmered in last October’s spotlight across four relief appearances -- will be a much-needed shot in the arm for a Red Sox club that can’t afford many more missteps.

COULD STILL RETURN IN 2019

Tyler Glasnow, Rays
Likely return: September

Remember that xwOBA list we referenced earlier with Clevinger? Glasnow tops it, and he was the American League’s ERA leader when he went on the IL with a right forearm strain on May 11. The Rays were hoping Glasnow would be back as soon as this weekend before he suffered a setback last month, but he’s still confident he can return in 2019. Tampa Bay can’t necessarily count on that, given that this is an arm injury, but a potential September rotation of Glasnow, Blake Snell, Charlie Morton, Yonny Chirinos and Brendan McKay could be a difference maker in the AL East and Wild Card races.

Dellin Betances and Luis Severino, Yankees
Likely returns: Betances -- late July or August; Severino -- early September

Severino’s setback last month wasn’t encouraging, but he's been cleared to start a throwing program this week, and GM Brian Cashman maintains confidence that he’ll return this season. The Yankees will probably try to acquire arms regardless of whether Severino returns, but if he does, that means New York adds MLB’s hardest-throwing starter from last year -- either to its rotation or its bullpen.

Meanwhile, the Yankees’ ‘pen already leads the Majors in fWAR and ranks third in strikeout rate, and it could still add one of the greatest strikeout relievers of all time in Betances, who has also been cleared to begin throwing along with Severino. It’s still difficult to tell when Betances could return from his lat strain, and his command issues will always be part of the story. But this Yankees bullpen is strong enough to weather that; his addition would file firmly under “the rich get richer.”