Ranger Suárez has made four rehab starts since beginning a minor league assignment three weeks ago. That includes 4 2/3 innings of one-run ball for Triple-A Lehigh Valley over the weekend. After building to 78 pitches, he’ll make his return to the majors this weekend. Manager Rob Thomson told reporters (including Lochlahn March of The Philadelphia Inquirer) that Suárez will be activated to start against Arizona on Sunday.

That may push Philadelphia to a six-man rotation. Thomson acknowledged yesterday that the Phils were considering moving to a six-man staff rather than bumping anyone to the bullpen (link via Noah Levick of NBC Sports Philadelphia). Zack Wheeler, Aaron Nola, Jesús Luzardo, Cristopher Sánchez and Taijuan Walker have combined for every Phils start this season.

Walker was the one who would have been ticketed for the bullpen had Suárez been healthy. He’d be the candidate to move back to relief, but he has pitched fairly well through his first five starts. Walker owns a 2.78 ERA across 22 2/3 innings. His 20% strikeout rate and 10% walk percentage are each a little worse than average, but he has allowed two or fewer runs in all but one of his outings. Walker has found a little extra velocity relative to last season. He’s averaging 92 MPH on both his four-seam and sinker after sitting around 91 a year ago.

Luzardo, Wheeler and Sánchez have all been excellent. Nola has struggled while operating with diminished velocity, but his rotation spot clearly isn’t any jeopardy. The Phils have already confirmed that Suárez will return to the rotation, while Sánchez’s recent forearm soreness seemingly amounted to nothing. The question is essentially whether the Phils feel Walker will be more valuable in a long relief role or taking the ball every sixth day.

Walker will make at least one more start. He’s tabbed as the probable pitcher tomorrow against Brad Lord in their series finale against Washington. Wheeler and Sánchez have gone over the past two days. The Phils will run with Luzardo, Nola and Suárez against the D-Backs. They’re off on Monday before a stretch of nine game days.

While the rotation has been a strength, Philadelphia’s relief group has struggled. Their bullpen entered play Wednesday with a 5.25 ERA that was better only the Nationals’ 7.47 mark. No bullpen has blown more leads than Philadelphia’s eight. José Alvarado, Matt Strahm and Tanner Banks (to a lesser extent) are the only Phils relievers who have pitched well. Righties Orion Kerkering and Jordan Romano, both of whom have worked in high-leverage spots, have each had particularly poor starts. Walker is unlikely to be an impact relief weapon, but he’d give Thomson another option in the middle to late innings if they move him back to the bullpen after tomorrow.