Flash forward a half a year later and the 23-year-old pitcher has continued to live up to that praise, and then some.
Wednesday night at Angel Stadium, Giles dispatched baseball's best position player in a six-pitch at-bat. Mike Trout didn't look comfortable at any point, really.
After beginning the at-bat in the seventh inning with a low slider that Trout laid off, Giles painted the outside corner with a 99-mph fastball. Then he threw another 99-mph pitch right down the heart of the plate, and Trout swung and missed.
Up 1-2, Giles dialed it up to 100 mph and Trout got just enough to foul it off. Trout then fouled off a slider.
Giles then ended the confrontation the same way he began it - with a slider that ended up outside the strike zone, both low and outside - and Trout went down fishing . . . er, swinging.
"He was impressive," Sandberg said of Giles, who retired all three hitters he faced in relief of A.J. Burnett. "Real good fastballs down, the breaking pitch. He had a solid inning there."
In his first 24 big-league games, Giles has struck out 37 of the 91 hitters he's faced (40.6 percent). Among major league relievers with at least 20 innings of work this year, Giles' 13.32 strikeouts-per-nine innings rate is ninth best in baseball.
Among those eight relievers ahead of Giles, only three have struck out a higher percentage of the batters they've faced this season: Cincinnati's Aroldis Chapman (53.2 percent), Atlanta's Craig Kimbrel (41.45) and Tampa's Brad Boxberger (42.85).
On Wednesday, Trout joined an impressive list of Giles' strikeout victims that includes Andrew McCutchen, Paul Goldschmidt, Carlos Gomez, Jayson Werth, David Wright and Giancarlo Stanton (twice).
Giles' devastating two-pitch arsenal - a fastball that regularly approaches 100 mph and a slider that darts away from righthanders a la Brad Lidge in his prime - is the recipe for his high strikeout rate. His regular success has only boosted his confidence.
Although his big-league career is barely 2 months old, Giles appears to be more than ready to step into the closer role.
But that's where the story gets complicated on a Phillies team where nothing can go quite right in 2014. Giles' progression from prospect to dominating bullpen presence is in a holding pattern.
Like Ryan Howard once upon a time with Jim Thome, and Chase Utley with Placido Polanco, Giles is blocked. Jonathan Papelbon is in the way.
Papelbon, 33, is in the third year of a 4-year, $50 million deal, the largest contract ever given to a big-league reliever. Papelbon is under contract for 2015 and can stick around until 2016, too, if a vesting clause in his deal (55 games finished in 2015 or 100 in 2014 and '15) is reached.
But that doesn't necessarily guarantee he'll play out the remainder of that deal in Philadelphia.
Papelbon said a month ago he'd happily accept a deal that would send him to be a closer on a contending team. The Phillies have attempted to trade Papelbon for more than a year.
His heavy salary and declining performance made him unattractive to potential suitors a year ago and over the winter. Although he no longer piles up strikeouts as he did in his early Boston years, Papelbon has rebounded this season and has proved he still has the closer bravado and the know-how to finish off a game.
Papelbon has converted 27 of 30 save opportunities this season. He hasn't allowed a run in 44 of his 49 appearances. He's given up only four extra-base hits (and one home runs) to 191 batters in 49 1/3 innings.
The Phillies almost certainly would take on some of his salary to consummate a trade, and perhaps the timing could finally becoming right for such a deal.
The Detroit Tigers have lost seven of their previous nine games, falling out of first place for the first time since mid-June. Detroit has four blown saves since the All-Star break. Its 4.35 ERA from the bullpen is the fourth worst in baseball this season.
Detroit traded for a closer last month, slotting Joakim Soria to a setup role in front of Joe Nathan. Soria was placed on the DL with an oblique strain last weekend and Nathan leads all regular major league closers with six blown saves.
Nathan, signed to a 2-year, $20 million deal this winter, has walked eight of the 28 batters he's faced this month and has ghastly ERA (5.11) and WHIP (1.57) numbers this season.
Having lost two World Series in the last 9 years, and falling in the ALCS 2 other years, the Tigers are clearly in all-in, win-now mode. They traded for David Price at the deadline. They need to maximize their chances of winning it all while Max Scherzer is under contract (he is a free agent after the year) and while Miguel Cabrera, Vic Martinez and Justin Verlander (all 31 or older) are in their prime.
Papelbon cleared waivers earlier this month. He can be traded to a contending team trying to finalize its playoff push at any time in the next 2 weeks.
Finding a trade partner probably still isn't as easy as calling up the Tigers and convincing them Papelbon is their guy. But finding the closer's successor in Philadelphia hasn't been difficult at all.
He's the guy who has been striking out perennial MVP candidates on a weekly basis for the last 2 months.
On Twitter: @ryanlawrence21