Waldron (oblique) has yet to resume throwing, per MLB.com.

EDGE Analysis

Waldron is dealing with a mild left oblique strain and is expected to begin the campaign on the injured list. He had been competing for the Padres' fifth-starter role this spring, though he struggled with an 8.68 ERA, 1.71 WHIP and 7:7 K:BB over 9.1 Cactus League innings before getting hurt. With both Waldron and Yu Darvish (elbow) likely unavailable at the start of the season, Randy Vasquez, Stephen Kolek and Kyle Hart are battling to fill San Diego's two available rotation slots.

Waldron suffered a mild left oblique strain while warming up in the bullpen Friday, Kevin Acee of The San Diego Union-Tribune reports.

EDGE Analysis

Waldron's injury prevented him from pitching as scheduled against the Rangers. He'll be re-evaluated Saturday, at which point a return timeline may be established, but his availability for Opening Day is currently up in the air. The 28-year-old right-hander has had a tough time getting going this spring, surrendering 11 runs (nine earned) on nine hits and seven walks while striking out seven batters in 9.1 innings.

Waldron didn't pitch as scheduled Friday due to a potential injury he suffered while warming up in the bullpen, AJ Cassavell of MLB.com reports.

EDGE Analysis

After Waldron threw a few pitches in the bullpen preparing for what was supposed to be his fifth appearance of the spring, a trainer intervened to check on him. The 28-year-old righty then retreated into the Padres' clubhouse. It's unclear at the moment what he might be dealing with, though more information is likely to be revealed following the game.

Waldron pitched three scoreless innings in a Cactus League contest against the Athletics on Thursday, allowing one hit and one walk while striking out two batters.

EDGE Analysis

Waldron's second spring start went very smoothly, as he allowed only three baserunners (one on an error), and two of those were wiped out on double plays. The knuckleballer has yielded just one run through five innings over two starts this spring as he makes his case for the fifth spot in San Diego's Opening Day rotation. Waldron's competition for that role includes Kyle Hart, Stephen Kolek, Randy Vasquez and Jhony Brito.

Waldron surrendered one run on two hits and no walks while striking out two batters over two innings in a Cactus League contest against Oakland on Saturday.

EDGE Analysis

Waldron is one of several pitchers competing for the final spot in San Diego's rotation, and he began his exhibition slate with a decent outing. After allowing a pair of hits and a run through three batters, the knuckleballer settled down to retire the final five batters he faced. Even if Waldron does land San Diego's fifth-starter role, he isn't a particularly intriguing fantasy option given his modest strikeout rate and 4.91 ERA over 146.2 frames last year.

Waldron said Wednesday that he is planning to throw his knuckleball more frequently during the upcoming season, AJ Cassavell of MLB.com reports.

EDGE Analysis

The knuckler was Waldron's most-used pitch last year, as he threw it 38.2 percent of the time, per Statcast. The right-hander registered a 27.5 percent whiff rate on the offering, and opponents had a .227 xBA against it, rendering it a relatively effective pitch, especially in comparison to his four-seamer (19.1 percent usage rate, 22.4 percent whiff rate, .247 xBA) and his sinker (14.3 percent usage rate, 6.7 percent whiff rate, .316 xBA). Waldron is battling for a spot at the back of San Diego's rotation, and how he -- and his knuckleball -- perform during Cactus League play could go a long way toward determining what his role will be at the start of the season.

Waldron was recalled from Triple-A El Paso on Sunday.

EDGE Analysis

Waldron will serve as fresh arm capable of logging multiple innings of relief Sunday following starter Martin Perez. Waldron, who is known best for his knuckleball, logged a 4.79 ERA, 1.24 WHIP and 130 strikeouts in 142.2 innings through 26 MLB starts this year.

Waldron was optioned to Triple-A El Paso on Thursday, Dennis Lin reports.

EDGE Analysis

Waldron has given up 22 earned runs across his last 14.1 innings spanning three starts and now the Padres will try to get him back on track in the minors. It's unclear who will take over Waldron's spot in the rotation, though Randy Vasquez is on the same schedule as Waldron and would be a natural fit to return to the majors.

Waldron (7-11) took the loss against Minnesota on Wednesday, allowing 10 runs on 12 hits and one walk while striking out three batters over 4.1 innings.

EDGE Analysis

Waldron managed to get through two scoreless frames before being tagged for a run in the third. He then fell apart in the fourth, as the Twins pounded him for seven runs on seven hits, including two doubles and a homer. Waldron was allowed to return for the fifth frame but retired just one batter before he was pulled after giving up another run, and the final tally against him came after he departed. The knuckleballer has been knocked around in each of his past three starts, giving up a combined 22 runs over 14.1 frames. HIs season ERA has jumped from 3.79 ERA to 4.79 due to the rough patch.

Waldron (7-10) allowed seven runs on nine hits and a walk while striking out six over 5.2 innings to take the loss Friday versus the Rockies.

EDGE Analysis

To his credit, Waldron mostly spared the Padres' bullpen after laboring through a four-run first inning that saw him throw 28 of his 102 pitches in the start. This was the third time in four outings he's given up at least five runs, and he's yielded at least one home run in nine of his last 11 starts after surrendering just six long balls over his first 14 appearances. Waldron has a 4.29 ERA, 1.19 WHIP and 127:39 K:BB through 138.1 innings over 25 starts this season. His next outing is projected to be at home versus the Twins.