Marquis will be making his third start for the Padres after an early-season flameout with the Twins that was preceded by a wrenching Spring Training when his young daughter was injured and had to be hospitalized for almost three weeks.
Harrison, meanwhile, is working on a streak of five straight quality starts and has been maybe the Rangers' most consistent starter while compiling an 8-3 record with a 3.54 earned run average.
Marquis took an extended leave of absence from the Twins in March when his daughter Reese, 7, was seriously injured in a bicycle accident, suffered internal bleeding and was hospitalized and had to be sedated for nine days.
Reese has recovered nicely, but the incident threw Marquis behind in his preparations for the season and he started the season with Double-A New Britain while working to get his pitch count back up.
He never was able to figure things out and the Twins, who signed him to a one-year deal worth $3 million, released him after seven starts. His record with the Twins was 2-4 with an 8.47 ERA.
Marquis hurt himself with a throwing error in an 8-3 loss to the Giants in his first start for the Padres June 7, but was impressive in his second start Wednesday against the Mariners.
He worked 6 1/3 scoreless innings, allowing six hits in a 1-0 victory over the Mariners.
Marquis, who has played for eight big league teams in his career, takes ownership of his struggles with the Twins and is happy to be getting another shot with the Padres.
"I don't want to sit here and make excuses," he said. "I just didn't pitch well.
"As you get older, you work on things and figure things out during Spring Training. I wasn't able to do that."
Padres manager Bud Black was appreciative of Marquis' effort against the Mariners.
"Jason did a nice job keeping the ball below the strike zone," Black said. "He kept the ball at the knees when he needed to throw a strike. This guy is a veteran pitcher who has had success and knows his game."
Harrison starts Monday's game working on a string of 16 1/3 scoreless innings after following his third career shutout June 8 against the Giants with 7 1/3 innings Wednesday in a no-decision against the D-backs.
Harrison has credited his recent success to his ability to relax, not overthrow and maintain command of his pitches.
There was more of that in the start against the D-backs, he said.
"I thought my aggressiveness and tempo were a lot better," Harrison said. "[Catcher Yorvit] Torrealba called a great game. I was just focused on hitting his mitt and letting him call the pitches. We were on the same page."
Harrison did not want to come out of Wednesday's game while pitching another shutout but said he understood the move by manager Ron Washington.
"That situation right there, with it 0-0 and two righties coming up, it was the right move," Harrison said. "You never want to come out of the game, but it was the right move."
Rangers: Gentry stays hot
Center fielder Craig Gentry had two more hits in Sunday's 9-3 victory over the Astros, raising his batting average to .349.
Padres: A winning road trip
With Sunday's 2-1 victory over the A's, the Padres concluded a nine-game road trip with a 5-4 record. It was their first winning road trip of the season.
In the 17 games prior to Sunday, the Padres' offense had picked up to the tune of a .252 batting average (145-for-576) with 33 doubles, 11 triples and 18 home runs.
That didn't continue Sunday when they managed to win despite getting only five hits.
The series with the Padres will mark the return to San Diego of Rangers reliever Mike Adams. Adams was one of the dominant setup men in the National League when the Rangers acquired him at the Trade Deadline last season.
"It's going to be a lot of fun," Adams said. "I'll see a lot of faces that I have been around the past 4 1/2 years and it will be exciting to pitch back in San Diego."
Adams has been good, but not dominant for the Rangers like he was for the Padres.
"I don't think I have truly pitched the way I'm capable," he said. "There is a lot more to do. It has been mostly mechanical issues, not performance. I'm trying to get better and make adjustments so I can be more consistent."