Appellant Guillermo Plata-Mora, through counsel, appeals his 168-month sentence for conspiracy and possession with the intent to distribute five kilograms or more of cocaine while aboard a vessel subject to the United States jurisdiction, in violation of 46 App. U.S.C. § 1903(a), (g), and Q) and 21 U.S.C. § 960(b)(l)(B)(ii). On appeal, Plata-Mora argues that the district court erred in denying his request for a mitigating-role reduction. He also argues that the court committed reversible error under Blakely v. Washington, 542 U.S. 296, 124 S.Ct. 2531, 159 L.Ed.2d 403 (2004), and United States v. Booker, 543 U.S.-, 125 S.Ct. 738, 160 L.Ed.2d 621 (2005), when it sentenced him under a mandatory Guidelines system.
Mitigating-Role Reduction
“[A] district court’s determination of a defendant’s role in the offense is a question of fact to be reviewed under the clearly erroneous standard.” United States v. De Varon, 175 F.3d 930, 938 (11th Cir. 1999) (en bane). A defendant who is “plainly among the least culpable of those involved in the conduct of a group,” is entitled to a four-level reduction for his minimal role in the offense. U.S.S.G. § 3B1.2(a), comment, (n. 4). A defendant “who is less culpable than most other participants, but whose role could not be described as minimal” is entitled to a two-level reduction for his minor role. U.S.S.G. § 3B1.2(b), comment, (n. 5). “The proponent of the downward adjustment ... always bears the burden of proving a mitigating role in the offense by a preponderance of the evidence.” De Varon, 175 F.3d at 939.
In De Varón, we established a two-part test for whether a mitigating-role reduction is appropriate. See id. at 940-45. In applying the first prong, “the district court must measure the defendant’s role against the relevant conduct for which [he] has been held accountable.” Id. at 940. “[W]here the relevant conduct attributed to a defendant is identical to [his] actual conduct, [he] cannot prove that [he] is entitled to a minor [or minimal] role adjustment simply by pointing to some broader criminal scheme in which [he] was a minor participant but for which [he] was not held accountable.” Id. at 941. “[W]hen a drug courier’s relevant conduct *135is limited to [his] own act of importation, a district court may legitimately conclude that the courier played an important or essential role in the importation of those drugs.” Id. at 942-43. Critically, the first prong of De Varon is often dispositive. See Id. at 945. “Only if a defendant can establish that [he] played a relatively minor role in the conduct for which [he] has already been held accountable ... should the district court grant a downward adjustment for minor role in the offense.” Id. at 944.
In the second prong of the De Varón analysis, the district court may assess a defendant’s relative culpability vis-a-vis “other participants in the relevant conduct.” “The conduct of participants in any larger criminal conspiracy is irrelevant.” However, “[t]he fact that a defendant’s role may be less than that of other participants engaged in the relevant conduct may not be dispositive of role in the offense, since it is possible that none are minor or minimal participants.” Id. The district court has “considerable discretion in making this fact-intensive determination.” United States v. Boyd, 291 F.3d 1274, 1277-78 (11th Cir.2002).
Here, the record supports the district court’s findings that the conduct attributed to Plata-Mora was identical to his actual conduct and that he did not demonstrate that he was less culpable than his codefendants. Accordingly, we conclude that the district court did not clearly err,'and we affirm its denial of Plata-Mora’s request for a mitigating-role reduction.
Blakely/Booker
When an appellant has timely objected to the application of the Sentencing Guidelines, we review his Blakely/Booker claim “in order to determine whether the error was harmless.” United States v. Mathenia, 409 F.3d 1289, 1291 (11th Cir.2005).
A non-constitutional error is harmless if, viewing the proceedings in their entirety, a court determines that the error did not affect the sentence, or had but very slight effect. If one can say with fair assurance ... that the sentence was not substantially swayed by the error, the sentence is due to be affirmed even though there was error.
Id. at 1292 (quotations and alterations omitted). “It is as difficult for the government to meet that standard as it is for a defendant to meet the third-prong prejudice standard for plain error review.” Id. at 1292; see also United States v. Rodriguez, 398 F.3d 1291, 1301 (11th Cir.) (describing the defendant’s burden under plain-error analysis), cert. denied, — U.S. -, 125 S.Ct. 2935, — L.Ed.2d - (2005) (No. 04-1148).
In Blakely, the Supreme Court held that, under the state of Washington’s mandatory sentencing guidelines system, the imposition of a sentencing enhancement based upon facts neither admitted by the defendant nor found by the jury violated the defendant’s Sixth Amendment right to a jury trial. 542 U.S. at-, 124 S.Ct. at 2534-38. In Booker, the Supreme Court extended this holding to the Federal Sentencing Guidelines. 543 U.S. at-, 125 S.Ct. at 760. To cure the Sixth Amendment violation in Booker, the Supreme Court (1) excised two statutory provisions that reinforced the mandatory nature of the Guidelines, (2) held that the Guidelines were advisory, and (3) determined that sentences should be reviewed on appeal for reasonableness, considering the 18 U.S.C. § 3553(a) factors.1 Id. at-, 125 S.Ct. at 764.
*136We have held that there could be two distinct Booker errors — (1) the error of imposing a sentencing enhancement based on judicial findings that go beyond the facts admitted by the defendant or found by the jury, or “constitutional error”; and (2) the error of being sentenced under a mandatory guidelines system, or “statutory error.” See Mathenia, 409 F.3d at 1291; United States v. Shelton, 400 F.3d 1325, 1329-1334 (11th Cir.2005).
In the preserved error context where the government bears the burden of proving that the statutory error is harmless, we have affirmed a defendant’s sentence, despite the Booker error when the district court stated its sentence would be the same even if the Supreme Court affirmed the decision in Booker and held that “under Blakely, the United States Sentencing Guidelines [were] unconstitutional.... ” See Mathenia, 409 F.3d at 1291.
Because Plata-Mora does not raise any constitutional Booker errors, our review is limited to whether the district court committed a non-constitutional Booker error in sentencing Plata-Mora under the Guidelines as mandatory. Because the district court sentenced Plata-Mora at the bottom of his guidelines range and did not offer an indication that its sentence would have been the same if the Guidelines were not mandatory, the government cannot show “with fair assurance” that the mandatory nature of the Guidelines did not substantially sway Plata-Mora’s sentence. See Mathenia, 409 F.3d at 1292. Therefore, we conclude that the statutory Booker error is not harmless.
For the foregoing reasons, we affirm the district court’s denial of Plata-Mora’s request for a mitigating-role reduction, but we vacate Plata-Mora’s sentence and remand this case for resentencing consistent with Blakely and Booker.
AFFIRMED in part and VACATED and REMANDED in part.