SF Giants need a spark, and a rotation shakeup could be the place to start

The San Francisco Giants have their backs against the wall, yet again. For the first time since July 2019, they're 10 games under .500. Their 20-30 record, following their 6-3 loss to the Diamondbacks on Wednesday, is the second-worst in the National League. Obviously, and unfortunately, miracle solutions to problems like this one don't exist. But a rational and proven way to right a sinking ship — or at least try to — is to shake things up, and the Giants are familiar with that strategy.

When the offense was hitting a new low every week, the front office elected to call up some reinforcements. While those reinforcements haven't made a huge impact, the offense as a whole is getting closer to what it should look like: from the worst one in the league to an average one over the last few weeks.

So why not do it again, but on the pitching side this time? One change in the rotation probably won't propel the Giants to the Wild Card spot they've been coveting for years now, but it might just be the start. And this change has a name: Trevor McDonald.

Logan Webb is set to be activated from the injured list soon after being placed on it on May 9 with right knee bursitis — basically inflammation in the knee. It marked the first time Webb had been placed on the IL in five years.

He had made 157 consecutive starts and had actually been dealing with the injury since the start of the season. But he aggravated it on April 30 in his start against the Phillies, and it showed in his ensuing outing, when he gave up six runs in just six innings against the Padres on May 5 — an underwhelming performance that elevated his ERA to 5.06.

But the 29-year-old ace is progressing well and on his way back. He threw a bullpen session on Tuesday in Arizona and will start his rehab assignment in Sacramento on Friday. He's expected to make just one start and could be back in the rotation as soon as late May. My guess would be either against the Diamondbacks in San Francisco or against the Rockies in Colorado.

A rotation decision is coming for the Giants and they must get it right

As you probably figured, Webb coming back and McDonald hypothetically incorporating the rotation means that a member of the current rotation will have to relinquish his spot.

First, let me make the case for why McDonald deserves that spot. Drafted in 2019, McDonald entered the 2026 season with just four major-league appearances, all in September. In his two starts in 2025, he allowed just one earned run — four total — in 13 innings against the Dodgers and Rockies. But when the Giants announced their Opening Day 26-man roster on March 25, his name was not on it, not even in the relievers column.

Instead, he started his season in Sacramento and put up relatively unimpressive numbers. He posted a 5.68 ERA in his four starts with the River Cats, though he allowed just seven hits. So when Tony Vitello called him up to use him as a spot starter against the Padres on May 4, McDonald was determined not to let this opportunity slide. Spoiler alert: he did not. He yielded just one run and became just the second starter this season — along with Landen Roupp — to give up just two hits through seven innings.

Then, Webb getting placed on the 15-day IL bought him at least three additional opportunities to prove he belongs among the big boys. So far, so good for T-Mac, as he allowed just four combined runs in 12 innings pitched over the first two of those three starts — three against the intimidating Dodgers in Los Angeles, and one against the Athletics in a stadium he's grown very familiar with: Sutter Health Park, the River Cats' home field.

He'll have one more shot to show his worth against the White Sox on Friday in San Francisco, though he probably doesn't have many people left to convince, if any.

So the Giants have a couple of routes to consider. The first is to incorporate McDonald into the rotation and move either Adrian Houser or Tyler Mahle out of it. The second is to stick with this group and send down McDonald, who still has options left.

The coherent and fan-clamored-for decision would be to go with McDonald. Even Mike Krukow is in favor of keeping McDonald in the rotation. If that's the case, one of the two starters the Giants acquired in free agency would lose his role. It doesn't necessarily mean he would be DFA'd. He could still serve as a relief arm or get traded if there are any relevant suitors and offers on the table.

This decision would have been much more difficult to make a few weeks ago, but Houser has made it seem more straightforward — and so has Mahle.

The Giants signed Houser to a two-year, $22 million contract during the offseason, so if they had to choose between him and Mahle — who signed a one-year, $10 million deal — to underperform, they would probably go with the latter. Strictly for financial reasons, the loss would be lighter.

So the way Houser has pitched lately must be a source of satisfaction. But it hasn't always been pretty for the 33-year-old. As a matter of fact, it's been problematic more often than pretty so far. Houser posted a 7.12 ERA over his first six starts, while pitching through the fifth inning just once.

But like I said, it's been better lately. Since the calendar turned to May, Houser has looked much more like the guy the front office thought they would get. His 2.04 ERA in May is among the best in the league, and he's allowed a total of just 10 hits and four earned runs over his last three games and 17 2/3 innings.

And if he can figure out a way to contain left-handed hitters, even just a little bit, his bad month of April could quickly evaporate into a bad memory. Houser has faced 125 lefties this season, and they've batted .356 with a 1.135 OPS against him. In other words, every time a lefty faces Houser, that hitter morphs into Barry Bonds.

Mahle's stuff has also looked pretty good at times, like when he threw seven shutout innings against the Dodgers or limited the Phillies to just three hits in 5 2/3 innings. But his low points have been as striking as his high points.

Through 10 starts with the Giants, Mahle owns the highest ERA (6.10) in the majors among qualified pitchers, the worst record (1-6), and the third-highest WHIP (1.57) in the National League. The concerning trend has been inconsistency.

When he's not throwing gems, he basically allows four or more runs, with no in-between. He's ended with five or more runs on his stat sheet in five of his 10 starts. In his latest outing against the Diamondbacks, he allowed six runs in just five innings — a steep hill to climb, even for this improved offense.

While Houser has had problems against lefties, Mahle's troubles have come when facing the order for the third time. His outing against the Diamondbacks on Wednesday was the latest instance.

Mahle entered the fifth inning with just four hits and two runs allowed — both on a home run — respectable numbers. But then came the fifth, and the top of the order for the third time. Mahle proceeded to give up three runs on four hits in the inning, giving Arizona a three-run lead it would never relinquish.

On the season, his numbers in those situations are just as alarming: a 9.00 ERA across eight innings in the fifth and a 16.88 ERA across 2 2/3 innings in the sixth.

If everything goes according to plan, Logan Webb will be back next week. That gives the Giants about a week to decide which route they want to take. Houser is scheduled to make a start on Saturday, and another strong performance could push Mahle out of the rotation for good.

Recent history has told us that Buster Posey and this front office aren't afraid to make meaningful moves when necessary. Now we're about to find out if the coaching staff is cut from the same cloth.

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